Following up: The issue turned out to be permissions on the database folder.  The SYSTEM account had no permission and since the Firebird service runs under the Windows System account, it needs permission. Adding Read/Write/Modify permissions resolved the issue.

Roger, one of my clients server crashed.  I installed Timeslips to a local workstation while they are off getting a new server.  It is a "home" computer.  Everytime I try to open Timeslips I get a message "The Firebird Database Engine has encountered an error - connection regjected by remote interface.  I have turned on and off the Firebird Service; I checked the permissions on System and there are full read/write rights for everyone.  I tried to research the error without success.  The client is currently on v2018 and will be upgrading to 2020.  Any ideas?

Did you do a full install of Timeslips on the local workstation, including the firebird server service? Can you open TSAdmin and check on the diagnose the computer and diagnose the server? On diagnose the server make sure port 4000 is open. On diagnose the computer make sure you have all green check marks. 

I suspect it is a firewall issue, Judy.  If they have an anti-virus/firewall solution, try disabling it temporarily and see if it works.  If it is only the Windows Defender firewall, be sure the port exception for port 3050 for Firebird exists - and if not manually enter it.

I suspect it is a firewall issue, Judy.  If they have an anti-virus/firewall solution, try disabling it temporarily and see if it works.  If it is only the Windows Defender firewall, be sure the port exception for port 3050 for Firebird exists - and if not manually enter it.