IDK if this will work for anyone else, but I fixed this by using regedit to edit the registry key:
And put quotes around the C:\Users\username\...\Now TV Player.exe path. Don't quote the entire key, just the path to the now tv player exe.
@winjer you genius!!!
I started a trial and couldn't get nothing (app or player to work) and doing this fixed it!!
You should let the techs for the app know because they couldn't recommend a decent fix for this issue. At least I can use the player now.. I still don't think I will continue after the trial because frankly everything should be maintained enough to work out of the box on any device without carrying out reg modifications and constantly uninstalling appdata files.
Well done though great find!!!!
Are you using the App from the Windows Store?
Or are you using the executable downloadable from the link on this web page?
Basically the App from the Windows store no longer works and you have to instead use the executable linked from the help page which will open & play the programs you select from this website.
NB: If you previously used the Windows Store app you may have to remove it from your device list before you can add the Windows Executable player as a new device if you are close to your device limit.