Is the tv connecting wirelessly?
That sound fine to be extra sure use it on lan for now, is the other end plugged into wan?, on the flint 2?
If all is fine, on the status page of the flint 2 you should now see it resolves the dhcp ip of the nighthawk, theoretical you should then have internet, if there is not a ip my suspicion points to a dhcp conflict you need to set a different lan ip range then.
If you can show logs (please post the last 10-20 lines of the log), maybe something interesting shows up.
As markdown you can use:
[details="click to expand"]
```
//Log
```
[/details]