@Liryc 

Hi,

Please run the command      and then compare the IP address shown by ping with the "Internet IP address" displayed by your router (circled in red in the sample screenshot below).

Are both IP addresses identical?

  @Liryc 

Ok.

After you have started the Wireguard connection on your phone, can you see an entry for an active WireGuard VPN Connection on the AX72 Pro in the menu "VPN Server -> Connections" ? 

  @woozle No, nothing shows up in the Connections page.

  @Liryc 

If you open the log of the Wireguard app on your Android phone, can you see messages like "Handshake did not complete after 5 seconds, retrying" ?

  @woozle Yes, that error appears in the app log

  @Liryc 

That means the WireGuard client cannot reach the WireGuard server.

One reason could be that the router is not reachable from the Internet, but you have already mentioned that you can reach devices on the router's local network from the Internet.

Another reason could be that the WireGuard service is not (properly) running on the router. What you could try is to switch off the WireGuard server and then switch it back on. If that doesn't help reboot the router. If both things don't help, then I think the next step would be to try a Factory Restore, but of course that can be quite an effort, because you would need to configure the whole router from scratch again.
 

  @woozle Tried restarting the routerand the VPN server with no succes.

Is there a way to check if the wireguard service is running?

  @Liryc 

Routers made by the major consumer brands typically don't allow direct access to the operating system (Linux in most cases) and therefore we have no way of checking which services are running or what messages are written to the log files.