I wanted to put this on here because I was losing my mind trying to get it sorted the past few weeks.
I moved house about 6 weeks ago and switched my ISP to Gigaclear (only providers in the area). I realised that my remote access was not working, and, on some devices, I couldn’t connect even from within the network, but it would go green for remote access then shortly after turn red and I was getting a Double-NAT message come up. I had the port forwarding setup, I checked all the recommended settings on the Linksys account, most were suggesting to put into bridge mode but the Gigaclear setup doesn’t support that as the Linksy acts as the main router, so I didn’t really have any other options. Then I saw a post on another forum about Double-NAT affecting their Xbox and the solution was to call Gigaclear directly and ask for a static IP, which I did and so far it seems to have worked! I had to speak to the loyalty team to set it up, it’s not something that can be solved with a quick email unfortunately.
They also said that it was a £2 a month rental fee for the static IP, but I told them I know people that have not had to pay that and they took it off straight away so make sure not to let them charge you for it!