invalid indentity public key

when i try to connect to a server, it says "connecting to external server", then I get a message that says "invalid identity public key". my wifi is ok and I've never received this message before, even when I had bad wifi. I've tried to connect multiple times but it keeps saying the same thing. i restarted Minecraft, nothing. then I tried to connect yet again, and it said I need to authenticate to Microsoft services. 

i get 5 messages when trying to join a server

-invalid identity public key

-you need to authenticate to Microsoft services

-disconnected from server

-sorry, we couldn't validate your login

-you must be logged in to XBL!

I've never gotten these messages before, I'm logged into my Microsoft account, so I don't know why its telling me these things