Your ISP has nothing to do with this. Your router will likely get a dynamic EXTERNAL address which has nothing to do with your internal addresses.
If you've reconnected the PC to the router and NAS to the router and now it's not working, you know the problem isn't with your NAS but with your network. I'd suggest reading your other posts if your only issue is not being able to access the NAS by name, to use the IP instead which is far more reliable.
I think you should continue this conversation in the other thread.