I can help you with resolving the error you're having when trying to log in to the account as the master admin, @Nadine V.
To resolve this, you can log in to the account as the admin or ask any admin of the account to remove your accountant access from the Accounting firms tab. Once done, clear your browser's cache before signing back as the master admin.
If you haven't deleted your accountant access yet or you want to verify if it's been removed successfully, check out this article for detailed guidance: Invite an accountant to review your books in QuickBooks Online.
Once done, clear cache and cookies to delete browser cache and Intuit-specific cookies to fix issues when using QuickBooks Online. There are times that the browser you're using has information stored that's stopping or causing the error when logging in to the account.
For more information on how to customize each user role or permissions in your account, refer to this article: Add and manage users in QuickBooks Online.
Let me know if you need further help to log in to the account as the admin by leaving a reply below. Have a great rest of the day!
