I've checked our records and there's no reported case where customers can't log in or access their QuickBooks Online (QBO) account. The problem you're having right now could be caused by the browser. Too much cache build-up in the program can result in unexpected product behavior. This could be the cause of your inability to access QuickBooks.

Let's run some basic troubleshooting steps to fix it. To begin, open a private window and log into your account. In Google Chrome, it is known as Incognito mode. This will assist us in isolating the problem and logging into the program. Simply press the following shortcut keys:

Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox).
Control + Option + P (Safari).

If you're able to successfully log in to QuickBooks, go back to your regular browser and clear its cache. Or else, use another supported browser instead. This might be a temporary issue with QuickBooks and the current browser that you use.

Additionally, feel free to visit the articles below on how to handle your Intuit logins, user management, company information, and other related matters:

I'd like to know how you get on after trying the steps, as I want to ensure this is resolved for you. Please reply to this post and I'll get back to you. Take care always.