Error while connecting to server via ISDN modem Dial up conectivity

[Kripal_1]

Hello!!

While other users try to connect to my server "remotely" using ISDN dial up they get the following error:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Error connecting to Dial Up
Checking Network protocol connections
TCP/IP CP reported error: 738. The server did not assign an address.
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SERVER DETAILS:

HP-UX , B.10.20 A 9000/785

US robotics Modem is connected to server and ISDN port.

I can login normally without any problems through local dial up.
Please help.