An application error has occurred while processing your request : -90

I appreciate you taking the time to perform all the troubleshooting steps to isolate the issue, Paul. Let me share the possible reason why you're encountering this error message in detail.

Typically, the error message signifies that the user role in QuickBooks Online (QBO) has certain restrictions on access. To ensure that you can overcome this issue, it is important to log in to your QuickBooks account as the Company Admin, as other user roles have limitations on permissions granted.

If the problem persists even after logging in as the admin, I suggest trying an alternative browser or opening a private window. Once you are able to complete your tasks in QBO, you can go back to your original browser and perform some troubleshooting steps, such as clearing your cache and cookies, to remove any site data that may have caused the problem.
 

However, if you're not assigned to the role, I recommend reaching out to your company admin and requesting them to modify your role and access permissions. By doing so, you will be able to perform your tasks in QuickBooks smoothly.

You can also check out this article to learn how to give primary admin rights to another team member in QuickBooks: Change the primary admin user in QuickBooks Online.
 

I'm still open and ready to answer any questions you may have with user roles or even running reports. I'm just a comment away always.