Synology RT2600ac VPN - cannot see any local devices
I'm using my iPhone (over 4G) to connect to my home network over a VPN configured using L2TP within VPN Plus Server (and then using the Standard VPN section). It connects, and I can access the internet, and if I lookup my IP address seen by the internet it's that of my home internet connection (ie. the same IP address I get at home if I google 'what is my IP address'.)
However, I cannot see any devices on my local network, despite selecting the local network IP range option, and my device having a local IP address on the same subnet as my home network. I cannot ping any local devices.
I've spent a long time googling for solutions - some appear to be complex which I'm assuming shouldn't be necessary.
Any tips? I was under the impression this should work automatically.