Our iPad pros and iPhone Xs all connect just fine. I was just surfing on the Mac and it just quit. Any ideas?

A few questions first:

• Does the affected Mac connect to other wifi networks with success? If yes, we know your Mac is ok and generally the software is working as expected.
• Are you close enough to the wireless network in question when testing connectivity?
• Have you already restarted the router or unplugged it from power and let it sit for a minute before plugging it back into power and then trying again.
• Remove and add back the affected network from the Preferred Networks list found in System Preferences > Network > Wi-Fi > Advanced

You could, as Dave mentioned, remove entries in Keychain having to do with the said network.

I can't think of any other steps right now but you could try this:

1. In the Finder go the Go menu and choose "Go to folder…"
2. Paste the following into the resulting text field: /Library/Preferences/SystemConfiguration.
3. Locate all the files inside the folder (path noted above) that have network or Wi-Fi in their filenames and move those to the desktop (don't leave copies of them behind in the folder). Some of those files may include names like: com.apple.airport.preferences.plist
   com.apple.network.eapolclient.configuration.plist
   com.apple.wifi.message-tracer.plist
   NetworkInterfaces.plist
4. Restart your Mac
5. Then try to connect to Wi-Fi again.
6. Reset SMC if all else fails.

Report back if issues persist.

What happens if you go into Keychain Access and remove the password for that Wi-Fi network? There might be multiple entries there to remove.

The other thing to try, albeit more of a pain, would be changing the Wi-Fi password itself on the router.

theres something about this that reminds me of another thread with network drive issues.

Thanks Dave. I’ll try those. I discovered something else. I opened Network Preferences and when I try to login to a wireless network from there, I get a “No IP Address found”. (See attachment)

Oh very interesting. That shows that your computer thinks it's connected to Wi-Fi (and authenticated, with the password), but can't get communication from the router's DHCP server.

Is it possible the router is denying requests? And is PixieHollow-Biz2.4 the right network?

Lastly, try highlighting Wi-Fi on that screen and clicking the minus sign to remove it entirely, then click plus and re-add Wi-Fi. Sometimes that can help, too.

I’m not sure. Our iPad Pros and iPhone Xs are all attached to that network and working flawlessly. 

I tried deleting that WiFi and adding a new one and that didn’t work either.

I don’t think it’s the network because I’m getting the same results when trying to join other networks, as well.

Notice it shows “Invalid Password”. I am positive I am using the correct passwords for these networks. Confused...

Does the wifi work on another account on the same Mac? If so, then it's likely some software problem in your account.

If it doesn't, you may have a hardware problem. (Or else something deep in the operating system is affecting all accounts.)