There should be a line saying which UPnP port was acquired, also make sure it connects to the right device given there are two.
[6TQJ3] 22:03:51 INFO: Created UPnP port mapping for external port 50131 on UPnP device 'FRITZ!Box 6340 Cable (kbw)' (192.168.178.1).
Can confirm this in the router
Then try accessing that port from the outside and see if it’s actually open. Is that definitely your gateway, given there are two routers on the network?
I just have this router and I tried a telnet from outside the network on this port and it was working.
Then try running with STTRACE environmwnt variable set to discovery and see what IP other nodes discover for this device, and make aure you can telnet from other devices.