Your port forwarding setup should be in the router settings.
And the port forwarding settings in your router should be set to affect a specific IP address that is assigned to your computer and that IP address should be manually set as a static IP address on your PC.
If you did a clean install of Windows then the static IP address settings in Windows got reset to automatic.
If you don't remember the static IP you set up, then go into your router settings, go to port forwarding, then see which IP address has the minecraft port being forwarded, then set that as your static IP in IPV4 settings of your computer's network adapter.
In regards to NAT, there is sometimes an option for NAT settings in routers depending on the router.
Otherwise, you need to use a good DNS service.
Google's DNS is good.
Primary DNS: 8.8.8.8
Secondary DNS: 8.8.4.4