Hello sarahcook173,
Welcome to Community! BMO has switched to OAuth to improve banking for QuickBooks Online customers. This has created a level of concern for many of our customers, who can't reconnect with BMO. I'd be happy to assist!
If you're a BMO Business user with chequing, savings and credit card accounts, you must login through a debit card. However, it has been reported by other QuickBooks customers, that error messages are being received. For this reason, I recommend contacting our Customer Care team at 1-855-253-1536 from Monday to Friday between the hours of 9 AM and 8 PM EST. They will be able to work with you in real time and assess the errors you're getting. In addition, they will be able to escalate the issue to the QuickBooks Development Team, for further investigation and resolution, so you can get back to business as soon as possible!
If you have any other questions, please feel free to reach back out. We would be glad to help!
