There’s no “can’t”. A holding action would be to take the old app and the new app, and bundle them together with a switch that tests your iPad OS version, and routes you to one or the other.
This would make the app just over twice as big, but it’s the ‘in extremis’ fix.
Though I think NowTV will work very hard to fix it properly, long before any court date could be set for any sort of fantasy legal action over this.
I posted this https://community.nowtv.com/t5/Mobile/iPod-5-iOS-9-3-5-fails-to-play/m-p/513841#M3719 this morning - I didn't have time to read all this thread as it was titled "iPad" but now reading it I would say that my issue is the same
Yes, it would seem that the updated iPad app only works on iPadOS 13, when the published information says it should work on any iOS from 9 onwards.
This may not be trivial to fix, but even if it is, the testing will be doubly stringent this time. So probably not a thing that can be rolled out in a few days 😥
But those who can upgrade to iPadOS 13 might like to consider doing so to overcome this issue right now, rather than waiting for the proper fix.
Disclaimer: I’m not an employee of NowTV, I’m just a customer like you, so I have no idea what progress is being made on this issue, and the first I know it is fixed will likely be when you know. And I’m not making any special pleading for NowTV here; just basing this on my own experience as a software developer, albeit in an unrelated feld.