So the player works great otherwise, but I'm wondering if there is just an easy fix to this? Maybe I can force reauthentication somehow.
I have the same problem.
It might just be youtube servers having some downtime. If it still happens now tho you can try the following.
Right-click anywhere inside the app and select "inspect element". Go to the console tab and type logout(), press enter.
The console tab also shows error that happened during loading. Are there any errors that don't start with "chrome-extension"?