Not sure exactly when - a month or so perhaps - but there has been a regression with regard to this capability. It almost never prompts to watch an active recording from the beginning or to watch live.
Here’s a link to the previously reported issue: Watch Recording prompt no longer happens for live TV events on tvOS
As you can see in that thread, it was resolved.
If you’re sure it’s not working, could you try some old beta builds to track down which one starts acting bad for you? Find a build that works, and move forward one by one until it breaks, and let us know the build number.
Yes, I know it was resolved. I was a part of the thread back then.
Unlikely that I’ll have time to do what you asked anytime soon. Been very busy lately and will continue to be for the foreseeable future. Thus, why it’s taken me a while to even report the regression.
I hadn't seen any issues with this recently but haven't really watched a lot of TV lately, so I ran a deliberate test and it worked fine for me