I'm here to help fix the issue you're having with your Supplier tab in QuickBooks Online (QBO).
Did you receive some error messages? Any additional information will help me provide the best resolution for your concern.
In the meantime, let's sign in to your QBO using a private browser (incognito). There are times that the browser is already full of frequently accessed page resources (cache and cookies), causing some unusual responses. Here's how:
Press Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox).
Control + Option + P (Safari).
Ctrl + Shift + P (Microsoft Edge)
Once logged in, go back to the Supplier tab again to double-check. If everything looks good, return to your default browser and perform a clear cache to refresh the system. However, if the issue persists, try using other supported browsers.