Steps followed

1) Log in with microsoft account (McSquawk) via the default minecraft launcher java version on Windows 10

2) Join standard private server that uses the standard minecraft server from https://www.minecraft.net/en-us/download/server  minecraft_server.1.16.4.jar 

3) Tried to send message or type command ('t' or '/')

Expected results

Able to type commands or chat

Actual results

Red "Cannot send chat message" message

Notes

The chat setting is set to "shown", also tried changing that, erasing the .roaming folder and  reinstalling the game. I tried logging in from a different computer and was still unable to press t or / . Other people joining the same server are able to do both.

EDIT

This ended up being because of the xbox settings here https://account.xbox.com/en-us/setting - probably needs a better error message