Incident : esxi 4.x lun not detected.

Issue : Some of the esxi 4.x hosts arent seeing 2 luns.
What we tried:
suggested to connect to the host via vSphere client bypassing the vCenter server and try adding the luns retaining the same signature but it only gives an options to reformat it and the re-signature options are grayed out.
fdisk -l /vmfs/devices/disks/naa.<xxxxxxx>. The partition table was listed as vmfs (confirming whether the partition table was corrupt or not and it was not corrupt)
esxcfg-volume -M naa.<xxx> but it said no matching naa.<xxx> found!.
~ # esxcfg-volume -l
VMFS3 UUID/label: <xxxxxxxxxxxxxxxxxxxxxx> /NAS_ESX2
Can mount: Yes
Can resignature: No (the volume is being actively used)
Extent name: naa.600508b4000ad2c800004123452345346:1     range: 0 - 511743 (MB)

VMFS3 UUID/label: <yyyyyyyyyyyyyyyyyyyyyyyyyy>/NAS_ESX1
Can mount: Yes
Can resignature: No (the volume is being actively used)
Extent name: naa.600508b4000ad2c80000478675676578787:1     range: 0 - 511743 (MB)

~ # esxcfg-volume -M <xxxxxxxxxxxxxxxxxxxxxx>
Persistently mounting volume <xxxxxxxxxxxxxxxxxxxxxx>
~ # esxcfg-volume -M <yyyyyyyyyyyyyyyyyyyyyyyyyy>
Persistently mounting volume <yyyyyyyyyyyyyyyyyyyyyyyyyy>
issue resolved.