Hi, @rooz999! I've got some steps you can perform to isolate the issue.
First, let's try opening your account through an incognito window to rule out the possibility of a webpage issue. Refer to these shortcut keys to open an incognito window in all supported browsers:
- Chrome: Ctrl+Shift+N
- Firefox: Ctrl+Shift+P
- Safari: Command+Shift+N
Once logged in, try connecting the app again. If it works, you may have accumulated too much historical data. I recommend clearing your browser's cache to access QuickBooks with a clean slate. You can also use a different supported browser.
If you're still getting the same error message, contact our Intuit Developer Team for further help. You can submit a case using the instructions below:
- Go to this link: https://help.developer.intuit.com/s/.
- Scroll down until you see "Can't find what you're looking for."
- Click the Contact Support blue button.

- Create a case by selecting a product and category first. Then, Next.
- Follow the onscreen instructions.
I'll be right here if you need a hand with anything concerning QuickBooks. Have a great day, @rooz999!