Have you tried accessing your account via a private browser? If you haven't, please follow these steps so we can verify if it's a browse issue or not.
Press CTRL+SHIFT+N for Chrome.
Hold and press CTRL+SHIFT+P for Mozilla Firefox and IE.
Once done, go back to setting up your payroll item and tax tracking again. If it's working fine, you can clear the cache of your regular browser. This process will delete the temporarily stored file in your browser.