Login problems


I`m using Acucobol-Gt Thin client 80, and it`s saying:

"conection failed"-"Connection to server refused"
When I try to log on from some of my clientpc`s. The odd thing is that 1. W7 ok. 1 XP, ok. 1 w8.1 ok. 1 W7 refused. 1 w8.1 refused.
The only differense is the brand of Pc. HP seems to be the best.
I have a HP server running W server 2012R2. Is this a known issue?

Regards Guffen