> The system was working on Windows XP. I am thinking there might be ACL issues but I'm unsure.

Are you aware that on XP it was still possible to use named pipes for
connection, while in Vista and higher (including Server2012) you
*must* use TCP/IP and need to qualify an IP-Adress (alternatively
"localhost")?

This at least is the solution in some 90% of all cases where other
Firebird users are asking me.