I am getting the same issue with my account today, seems to have only happened recently. I have done similar to you in trying to remedy the issue by changing browsers etc.. to no avail.

ipad versions can run on both MacOS and VisionOS (if the functionality is supported on those platforms). You can test against VisionOS as it has a simulator like iOS/tvOS. Bit harder to test against hardware, if you don't have the funds to buy a Mac or Vision Pro device. You could ask someone whom does have a Mac/Vision Pro to test it for you, you would need their email address to add them to a test group for your app though (this would use the Apple Testflight approach.)