`Sessions should be nested with care. Unset $TMUX to force.` using Byobu and Fish load on boot

Since upgrading my server to Ubuntu 24.04 I keep being instantly logged out. When I connect with SSH, it just states [exited]. There seems to be no way of logging into my account anymore. It is a separate account to root - logging in as root seems to be fine. My account has Byobu and Fish shell set up to autoload on login. Restarting the virtual machine makes no difference, so it is not like another session exists. Is there anyway to resolve this?