Hi @karatzaferi,
Welcome to the Community. Allow me to chime in and share additional guidance on fixing the error when connecting to QuickBooks Online.
Since you can log in through the incognito window, the browser's cache may be full. It can cause unusual behavior in QuickBooks, like being unable to access an account.
I suggest you clear the cache data to get back on track. You should be able to access your account through a regular browser after you perform the recommended steps.
We also have a list of supported computer operating systems and internet speeds for optimal QuickBooks performance. I've attached an article you can use to learn more about it: System requirements for QuickBooks Online, Accountant, Payroll, and QuickBooks Self-Employed.
Please let us know if you need more assistance connecting with QuickBooks Online. We'll be happy to help you some more. Keep safe.
