Hello
Can you go to your Windows Settings > Accounts > Access Work or School (note, it is the briefcase icon, not the little person icon). Then see if the organization email address is still listed? If so, click on it and then disconnect it.
Restart the computer, then see if you can remove it. If it still won't let you, go to Settings > Accounts > Sign in options, scroll down to mid page, under "Additional Settings",Make sure "For improved security, only allow Windows Hello Sign-in for Microsoft accounts on this device (Recommended). " is turned OFF.
Then try again.