Hi! I'm the system admin for a small company and our accountant is have this exact same issue! Did you ever find a permanent fix? Every single time they go to login to Intuit (which is daily), it says "We can't find anyone with [email]", and so far I've had to go in and delete the browser site data for intuit every single time they want to login, and then it works, albeit with having to go through two factor authentication every time as well.