If you are having QBO logging problem account, you can try this steps to try and troubleshoot it. Make sure your internet connection is good to start with. Either clear your browser cache or switch to other browsers to log in from. If you had multi-factor authentication set up, double-check the code you received. Confirm that your browser and/or QuickBooks Online have also been updated. If you try this and you still cannot log in, reset your password or click the "I forgot my username" link on the sign in page. If this still does not help, you will want to reach out to QuickBooks support.