Can’t Upgrade Mac to macOS Sequoia 15.5? What To Do

To fix macOS 15.5 installation issues, start by trying the upgrade in Safe Mode, which clears out temporary glitches and may let the process begin properly. If that fails, use Terminal to fetch a different version of the installer—newer or slightly older ones often work better.

Some users have had success installing the OS to an external drive or a new partition on their internal disk, which avoids interfering with your current system. In worst-case scenarios, where the Mac becomes unbootable, a DFU Revive or Restore using another Mac and Apple Configurator can bring it back to life.

Let’s take a closer look at all the possible workarounds.

Error When Upgrading to macOS Sequoia 15.5: Possible Causes

For the most part, the issue seems restricted to Macs with M1 processors — including Pro, Max, and Ultra variants. That usually indicates localized bugs, but the exact cause isn’t known yet. However, some users with other Apple Silicon Macs have reported similar bugs. Also, there’s no indication Intel Macs are immune to the issues, either.

The symptoms may vary a bit. In some cases, users find error messages saying “installation failed” or “updates not installed“. The installation procedure, in this scenario, doesn’t even begin.

In other situations, the installation seems to go through. However, after several reboots, the Mac is left unusable. A message saying “the version of macOS on the selected disk needs to be reinstalled” appears, in this case.

Lastly, some users go through the installation procedure, but, in the final rebooting sequence, the upgrade fails. The process gets reverted, with the user finding itself back with the macOS version it had prior to upgrading.

How To Fix Problems Preventing Your Mac From Upgrading to macOS Sequoia 15.5

Since the issues above seem to have different causes, the solutions for each one vary as well. Check below some possible fixes, and see which one applies to you.

1. Upgrade in Safe Mode

The first suggestion is trying to install the upgrade using the macOS Safe Mode. This seems to be particularly helpful to Macs that aren’t able to even start the installation procedure.

When restarting in Safe Mode, your Mac performs a “self-cleanup” that may get rid of some issues preventing the upgrade. Here’s how to do that in Apple Silicon Macs:

For Intel Macs, it’s a bit easier. Simply turn your Mac on while holding the Shift key until the login screen appears. There’s a chance you’ll need to log in twice, but that’s it.

2. Try an Older or Newer Installer

Recently, Apple has issued a buggy macOS Sequoia installer, which prevented many users from upgrading. In that situation, upgrading to version 15.4 was virtually impossible for some people. However, other versions, like 15.3.2 or 15.4.1, worked flawlessly.

If you want to give this solution a shot, you’ll need to use the command line. Check below:

1. Firstly, check your currently downloaded installer for its version. The easiest way of doing that is through the App Store.
2. After taking note of the installer version, open the Terminal app and issue the following command:
   softwareupdate --list-full-installers
3. This will return a list of macOS installers. Take note of the version number, either newer or older, closest to the one your buggy installer has.
4. After that, paste the following in Terminal:
   softwareupdate --fetch-full-installer --full-installer-version [VERSION]
   Replacing [VERSION] with the version number you chose in the previous step.
5. When the new version finishes downloading, check if you still can’t upgrade your Mac’s Sequoia version.

3. Install to an External Disk

In a few cases, the installer may simply refuse to upgrade the current startup disk. A quick solution to that is connecting an external SSD and installing macOS to that drive.

Usually, you can do that using the Install macOS Sequoia app. If, for any reason, that doesn’t work, you’ll need to create a macOS USB install disk.

Creating a USB Installer

The procedure involves a few steps, but it’s pretty simple. Check below:

1. Make sure you have a USB stick of at least 16GB available. Though it’s recommended to use a USB 3.0 thumb drive, this is not mandatory, and a USB 2.0 should work. This will make the process significantly slower, however.
2. Download a macOS installer, if you haven’t done that yet. You can either use the App Store or the terminal commands from method #2.
3. While the installer downloads, open Disk Utility and format the USB drive to Mac OS Extended (Journaled), with GUID Partition Map selected under Scheme.
4. After the download finishes, go to Terminal and issue the following command:
   sudo /Applications/Install\ macOS\ Sequoia.app/Contents/Resources/createinstallmedia --volume /Volumes/[DISK NAME]
   Where [DISK NAME] is the USB stick you just formatted.
5. Restart your Mac, holding the Option key upon boot. Select the macOS installer disk. After that, connect the external drive you’ll install macOS to.
6. From here, the procedure is the same as when you reinstall macOS using Internet Recovery. Just make sure you’re installing to the external disk, not to your Mac’s internal one.

4. Partition Your Drive, Then Install to the New Partition

One method I find particularly useful is partitioning your internal disk, installing the new macOS, then restoring your data. That not only helps if you can’t install macOS Sequoia on your Mac, but prevents data loss during upgrades, too. One thing to consider is that you need to have at least half of your storage free to use that method.

Partitioning Boot Drive in Recovery

However, partitioning your startup disk is risky. To make things safer, you can do that in Recovery Mode instead. It’s also possible to partition with Disk Utility in the USB installer.

Simply open Disk Utility from the installer or Recovery Mode, then select your Mac’s internal storage. Create a new APFS volume, close Disk Utility, then run the installer, pointing it to the new volume.

NOTE

You may need to create a new APFS container, instead of just an APFS volume. The macOS installer will warn you, in this case.

Installing and Restoring Files, Apps, and Settings

After restarting several times, your Mac will display the initial setup window. Follow the on-screen instructions, and, when it offers to restore your data, select the older startup disk. If you have a Time Machine backup, you can choose that instead, but restoring from the internal disk is faster.

Erase the Older Installation

To err on the side of caution, I suggest you use your Mac for a couple of days, at least. This way, you can be sure the upgraded installation is bug-free, and know you’re safe from startup issues. After that, simply open Disk Utility on the new installation and remove the old APFS volume from your internal drive.

Try a DFU Revive or Restore

Failed installation attempts may corrupt your Mac’s firmware. For Intel Macs with T2 security chips, and Apple Silicon Macs, that means you’ll need a DFU revive or restore. Here’s how to do that:

1. You’ll need a working Mac, a USB-C to USB-C cable, and the Apple Configurator app.
2. Plug the USB-C cable into the bricked Mac’s DFU port. The other end can be connected to any the working Mac’s USB-C ports.
3. Enter DFU mode in the bricked Mac. The procedure is different for MacBooks and for desktop Macs.
4. The bricked Mac should appear on the working Mac’s Finder sidebar. Click on it.
5. Select Revive Mac… to start the procedure. Reviving should be tried first, because it’s faster, and doesn’t require wiping your Mac’s storage.
6. A progress bar will appear in Finder, wait for it to complete. The bricked Mac should restart. If it shuts down instead, turn it on.
7. Select the startup disk, and, if prompted, enter your login password. The bricked Mac should then finish booting normally, and be usable again.
8. If reviving fails, you’ll need to restore your Mac. Perform step #5 again, but, this time, clicking Restore Mac… instead.
9. After the progress bar finishes, turn the bricked Mac on if it shuts down, or wait for it to reboot.
10. If prompted, choose a language. Enter your Apple Account password, and wait for the restore to finish. On Intel Macs, you’ll need to select Install macOS to start the reinstallation procedure.
11. Set your Mac up. If you have a Time Machine backup, you’ll be able to restore it. After that, you can try upgrading macOS Sequoia 15.5 on your Mac again, using one of the previous methods.

OS upgrades don’t always go smoothly. Even so, most people should be able to install macOS Sequoia 15.5 without much hassle. If, this hasn’t been your case, at least there are quite a few ways to fix the installation issues.