Quickbooks Error H101, H202, H303, or H505
Make sure each client with quickbook installed (Not the server or where the QB Database is stored) has this set, choose File > Utilities If you see Stop Hosting Multi-User Access, select that option.
Now go to the server/computer with the Quickbooks Database files then open up quickbooks and open company file and go to choose File > Utilities > Select Host Multi-User Access and then you should be good to go.
Also check your firewall on the Quickbooks DB Server to allow these ports below.
Create a Outbound Rules then select TCP and in the specific local ports box, enter in the following ports:
QuickBooks 2014: 8019, 56724, 55358-55362
QuickBooks 2013: 8019, 56723, 55353-55357
QuickBooks 2012: 8019, 56722, 55348-55352
QuickBooks 2011: 8019, 56721, 55343-55347
QuickBooks 2010: 8019, 56720, 55338-55342