PowerPath/VE : lun 0 not visible or missing paths on ESX

There was probably a time when no lun 0 was allocated and a rule was manually added to avoid errors posted against a LUNZ device.

Check the Claimrules (localcli_storage-core-claimrule-list---claimrule-classall.txt in the vmsupport logs)

if you see something like 

MP            103  runtime  location   MASK_PATH         adapter=vmhba2 channel=0 target=0 lun=0
MP            103  file     location   MASK_PATH         adapter=vmhba2 channel=0 target=0 lun=0
MP            104  runtime  location   MASK_PATH         adapter=vmhba2 channel=0 target=1 lun=0
MP            104  file     location   MASK_PATH         adapter=vmhba2 channel=0 target=1 lun=0

then this is your issue. Claim rules were manually added which are prevented lun 0 from being configured by PowerPath.

Environment : 
Host OS : ESX any flavour
Host multipathing : PowerPath (any release)
DELL-EMC HW : any array. Will occur more on VNX / VPLEX / XtremIO than on another array. 

All the devices are correctly discovered down all the paths but 1, and it appears to be lun 0.

When looking at HostMultipathStateInfo.txt, for a good path we have :

HostMultipathStateInfo-16-MpathRuntime: vmhba2:C0:T0:L1
HostMultipathStateInfo-16-MpathState: active
HostMultipathStateInfo-16-MpathDeviceName: naa.60001440000000107034xxxxxxxxxxxx
HostMultipathStateInfo-16-MpathDeviceDisplayName: EMC Fibre Channel Disk (naa.60001440000000107034xxxxxxxxxxxx)
HostMultipathStateInfo-16-MpathAdapter: vmhba2
HostMultipathStateInfo-16-MpathChannel: 0
HostMultipathStateInfo-16-MpathTarget: 0
HostMultipathStateInfo-16-MpathLun: 1
HostMultipathStateInfo-16-MpathPlugin: PowerPath
HostMultipathStateInfo-16-MpathTransport: fc
HostMultipathStateInfo-16-MpathCompactTransport: san
HostMultipathStateInfo-16-MpathAdapterTransport: fc.5001438007xxxxxx:5001438007xxxxxx
HostMultipathStateInfo-16-MpathTargettransport: fc.5000144047xxxxxx:50001442axxxxxx

while for a problematic path (missing), we have :

HostMultipathStateInfo-5-MpathRuntime: vmhba1:C0:T1:L0
HostMultipathStateInfo-5-MpathState: dead
HostMultipathStateInfo-5-MpathDeviceName: fc.5000144xxxxxxxx:5000144xxxxxxxx
HostMultipathStateInfo-5-MpathDeviceDisplayName: notfound
HostMultipathStateInfo-5-MpathAdapter: vmhba1
HostMultipathStateInfo-5-MpathChannel: 0
HostMultipathStateInfo-5-MpathTarget: 1
HostMultipathStateInfo-5-MpathLun: 0
HostMultipathStateInfo-5-MpathPlugin: MASK_PATH
HostMultipathStateInfo-5-MpathTransport: fc
HostMultipathStateInfo-5-MpathCompactTransport: san
HostMultipathStateInfo-5-MpathAdapterTransport: fc.500143xxxxxxxxxx:500143xxxxxxxxxx
HostMultipathStateInfo-5-MpathTargettransport: fc.5000144xxxxxxxxx:5000144xxxxxxxxx

Because the Plugin is MASK_PATH, the device can't be seen

If rules have been added to the regular claim rules to mask lun 0, remove these rules, reload the rules and rescan the devices. Alternatively, the ESX host can be rebooted after removing the rules.