We'd want to make sure that we get this sorted out. Can you tell us if you're getting an error message when working or updating details in the Sales Tax menu? If so, a possible browser issue might be causing this. I'll provide some steps that can resolve common browser issues when working in QuickBooks Online.
First, use an incognito/private browsing session or a different browser. Follow these keyboard shortcuts to open an incognito session:
Ctrl + Shift + N for Google Chrome
Ctrl + Shift + P for Firefox
Control + Option +P if you're using Safari
Ctrl + Shift + P for Microsoft Edge
You can also use any of these browsers if you have them installed in your computer. Once done, check if you can already make some changes and if the error is gone.