IPSec VPN connects but no internet

[Kurai]

I have a IPSec VPN running on my GT-AXE16000 using build 3004.388.8 and my Android phone, a Samsung S21 Ultra, has been connecting to it just fine for months now until recently. No changes were made at the router end, nor my phone, yet when I connect to the VPN which does happen just fine, there is no internet traffic and the phone is effectively dead end. Why?

 

[Kurai]

Just as an update to this. I switched off the IPSec VPN server and switched to Wireguard and it works fine. The problem is clearly with the IPSec VPN itself, not my network configuration, phone, etc.