Compellent SC40 iscsi connectivity issue

Hi,

Hope someone can provide a little help, we have a Compellent SC40 which is out of warranty actually, below is the issue:

We have server on it that are currently connected and volumes are mounted via iscsi. From the host end, all iscsi controller IP are pingable, able to telnet the port 3260. One server suddenly got disconnected and when I tried to do some iscsiadm command so it can connect to the compellent iscsi ip, its disconnected at compellent, though to note, it can still telnet the iscsi ip on port 3260. Tried checking the logs and there are no errors showing related to controllers. If i tried viewing the server at compellent web ui, it says, server port status is up but connectivity is disconnected.

Any similar issue here that may be able to provide some clue what is the problem?