@GA_Polo OK, got it. I didn't know that you have a few router devices behind the ISP router. I assume you already did this to resolve the no-ip.com IP address: Can you make this change and test if...

@RFP "Isn't it strange that I can't "see" the C6 from the C80? It does not appear in the network map nor the DHCP Client List." Probably missing from the C80 network map, because of the WDS mode that...

That's the problem: You mean to plug an ethernet cable into the C6 WAN port, connect to C80 LAN port and configure an Internet access ? If I understood correctly, then using the WDS would be...

@RFP Yeah, that's probably because you are not receiving an IP address on the WAN/Internet port and the C6 doesn't believe it has an internet access. But don't worry, you have already admin access to...

@RFP Check this thread if you have enabled WDS via 5 GHz band. If the issue persists try to configure WDS via 2.4 GHz band and test again.

Resetting the C6 seems to be the only option to gain control of the router in that case. That's from an old FW version of C6, you may not have this option currently available.