There could be many things that are stopping your new server from picking up the LUN, and without a lot more info, it's difficult to guess at what might be the problem.
Generally, when I have issues getting a new server setup, the first thing I check is whether the hbas for your new server have logged into the filer. You can do this via the command line with:
fcp show initiator
Here's an example of what the output will look like:
MYFAS1> fcp show initiator
Initiators connected on adapter 0c:
Initiators connected on adapter 0d:
Initiators connected on adapter 0a:
Initiators connected on adapter 0b:
If you don't see your WWPNs logged in, then the next thing to check is the zoning on your switches.
If you do see your WWPNs logged in, but you don't see your igroups associated with them, then double check you got the WWPN correct in the igroup.
If you see your WWPNs logged in, and the igroup is associated with them, then there's probably a subtle misconfiguration somewhere that would take some time to track down.