When a user attempts to access a company file on a multi-user network and the program is unable to establish a valid connection, QuickBooks Error H505 occurs. Incorrect hosting settings, blocked communication ports, or missing network setups are frequently the causes of this issue. Make sure the server is the only one with hosting enabled, set up the firewall to permit QuickBooks access, and verify that QuickBooks services such as QBDBMgrN are operational in order to resolve the issue. Contact the QB support team at 1.855.738.2784 if you run into any problems.