streaming

1. I have a 2019 roku ultra connected by lan.  Also a tcl with a built in roku on wifi.  In both cases, after authorizing I get a message that I need a video subscription.  It never gets to the point where it asks for my account.  What to do?

2. I have a 2019 LG with xfinity stream app built in.  It says I have no purchases and doesn't further.  I have not moved or anything.  I see somewhere that I may need to clear my cache.  How do you clear a cache on a tv?