It looks like you’ve got a double NAT situation. Basically you have both the Technicolor Router and the Google Nest WiFi acting as a router. The easiest solution would probably be to see if you can set the Technicolor Router to something like “bridge mode.” Alternatively you could put your Google Nest into bridge mode.
You’ll find more details about this situation here: https://help.roonlabs.com/portal/en/kb/articles/arc-port-forwarding#Multiple_NAT