Make sure you are using the EECIS login/password, not the UD password, and that you are connected using the VPN. The Linux server is managed by the ECE IT folks. You can post the issue as a ticket here and the ECE IT will help resolve asap.
If you are unsure if your VPN connectivity is operation, you can ping the server and check. In windows, open cmd from start menu
In the cmd window, us command
ping cpeg424.ece.udel.edu
If you have connectivity, you would see successful ping results are shown in the screenshot below. Otherwise, you have issues with VPN or LAN.