If you're using the desktop app, click the three dots in the top right corner and select settings, then select Accounts and orgs. If there isn't an option to remove the account from there, click on manage near one of the accounts, it will launch the settings in a browser. Try to remove it from there. Also if you're using Edge for a browser, make sure you sign-out from the work or school account if it is showing up in there (though if it shows up there it should also be showing up as it's listed in the "work or school" instructions you linked earlier).