Error H505 in QuickBooks arises (like most H-Series Errors) when the user cannot access the company file (and sometimes an error H202 leads to H505), usually resulting from hosting or network issues. The error occurs while in multi-user mode, and QuickBooks can't communicate with hosting server (sometimes the Peer-to-Peer (or SMB share) hosting configuration may lead to similar issues). Error H505 could be resulting from incorrect access or configuration settings, network errors, or firewall / antivirus program interference. Resolving Issue H505 will generally consist of checking that QuickBooks is configured to host the users, checking the network, and checking firewall/antivirus settings. Users may just have to run the QuickBooks Database Server Manager to solve the issue (if it was user accessing the folder via the Server use the DbMngr to fix any issues and re-establish the connection).