NT 4.0 RAS with Win98 client

I have a Win98SE client using a P-to-P ISDN to connect to a NT 4.0 RAS server. From the server’s ISDN modem system picks up call, then from client side it says checking user name and password then disconnects. I have check user account and granted dialin access, checked RAS server’s IP for client. What other things should I check?