I lost RCS for most of yesterday on my rooted stock phone. After I realized what was going on I went into Magisk and saw that an update was available for Play Integrity Fix and that solved the issue. What I found most annoying wasn’t that it didn’t work, but that it broke in a way that seemed like it was working. Both myself and other people saw that we were connected/chatting via RCS and their messages sent just fine, but I didn’t receive them. Well, until I applied the update, then I got all of them.