Can't join my own realm

I Can't play on my own Realm that I bought because I'm on a 'Incompatible Client' But I'm on 1.16.5- It says I have to switch to the newest version and or Not a snapshot,

~So I Go onto 1.17. just to get the Message 'Incompatible Client, Please use 1.16.5'

Please I need help, I want to play with my Friends