The error happens if the internet connection is interrupted, forrest1. 

Aside from clearing the cache, we can also access QuickBooks through any of our supported browsers like Google Chrome, Internet Explorer, or Mozilla Firefox.

If the same thing happens, I'd recommend reaching out to us so we can check if there are issues with the server. Our Customer Support Team can also perform advanced troubleshooting steps. Please refer to the steps given by my colleagues above on how to contact us. 

If you have further questions, you can always post them here.