Removed account still asks for sign in

I had a school gmail account in thunderbird that I no longer have access to because I graduated. Once I lost access to the account, thunderbird would repeatedly ask me to sign in, so I removed the account through account settings -> account actions -> remove account. However thunderbird still repeatedly requests me to sign into the removed account. The account is no longer visible in the account settings sidebar, and I've also removed the account from my outgoing server settings, and from my saved passwords, but it still asks to be to signed in. This is preventing thunderbird from automatically updating emails, since whenever it checks for new messages it gets stuck on the removed account.