How to Fix QuickBooks Error H505?

https://quickbookhelpdesk.com/blog/fix-quickbooks-error-h505/

QuickBooks Error H505 is a common multi-user mode problem that can prevent a workstation from connecting to the computer hosting your company file. You may see the error when trying to open a company file or switch to Multi-User Mode. The error usually means that something is blocking communication between the workstation and the host computer. Incorrect hosting settings, firewall restrictions, network problems, or QuickBooks services that are not running properly can cause the issue.