I have never had that same error message, but I did just "Add Firewall port exception for QuickBooks". Hoping this solves my problem. It seems like the most logical solution that was suggested so far. Just running the tool hub or "fix my file" did nothing. I will try to post link for the firewall change. (starting at #3)
https://quickbooks.intuit.com/learn-support/en-us/help-article/multi-user-mode/set-firewall-security...
