We switched to Tmobile One Unlimited 55 a few days ago from 2 lines of our old Select Choice Unl TT+D plan. Since then he could no longer watch youtube videos when not on wifi. Youtube video thumbnails show all gray, and videos won't play. I'm using the other line of the same One Unlimited 55 plan, youtube and everything else work fine on my phone. Youtube worked fine on his phone before we switched. He's on iphone x. Here's a screenshot of our account.
Best answer by pekingduck69
Turns out it was the data stash I'm see under my online account. Basically all the streaming app/sites on the binge on list was not working. For some reason they don't see the data stash on their end. TForce was having trouble removing it too. So she suggested to temporarily switch my plan back to the old one and switch to one 55+ again. Which totally worked. It took a long time to figure out the issue but it's all good now. TForce has been really helpful, and thank everyone here for trying to help!