Gmail won't work in iPhone post iOS 15 update

My gmail would send me mail and now suddenly it doesn’t. It keeps saying I need to verify and enter my correct account information but I don't know how to do this. I tried to change my password but it still doesn’t work. I cant tell if I got hacked or something.. This is really confusing me. All I know is that I recently got the ios 15 update and I don’t know if that messed up some things on my phone?

[Re-Titled by Moderator]