I'm having exactly the same problems with Rel 15.4.1. My devices that won’t connect anymore are TiVo Romaio (I have to use my sister’s old iPhone to connect for the latest guide info) and my TiVo Stream 4K. So far all the apps on the TiVo Stream 4K are connecting except Netflix and YouTube. I can Chromecast for YouTube from my iPad but not for Netflix. When I called Apple, they just suggested doing a network reset through Settings/General but that didn’t help. I never called back.