Do you run the server in server/gateway mode?
What about the ip-adresses of the internal and the external net? They should be in different ip-areas, e.g. 192.168.1.x and 192.168.2.x
You told, that you can ping stations in the internal net, can you ping your external network device?
What about the configuration of the internet access?
For any help further detais are needed.
With regards
Karl W. Mueller