Some of the basic trouble shooting ideas:
1. Check whether you have added the filer details in Transport protocol settings.
2. Check in the disk management whether you are able to see the disks. If you are unable to see the disks then check you ISCSI connection.
3. Check whether you have the ISCSI session established from that particular host to the filer.
Hope this helps you to trouble shoot your problem.
Thanks
Suseendran