I read briefly about CGNAT, a d I think this is the case, checking the IP of my services with external services I get an IP different from the one I see in my machine. Tested more than one DDNS service and all updated my IP with the same “wrong” value.

How do I solve this? Should I contact my ISP and hope they can provide a solution?

I did this too, and my log always gets an OK. But the IP never changes.