Wireguard (wg0) not shown as interface?

I installed the LUCI Webgui additional to the regular gl-inet webinterface to check on the firewall.
Reason is, I can ping from the LTE router → WG-Network AND the LAN of the WG-Server
but not the other way around which would be the goal.

The wg0 interface is not shown at the LUCI-Network-Interfaces, but appears at the Firewall settings page.
Here the fw config:

This is how the LUCI config looks like:
interfaces: https://ibb.co/n0rbNfm

firewall:  https://ibb.co/Vx0Yzd1

thanks for your help

Which router?

Can you see wg0 when using “ifconfig” when ssh to the router?