This issue occurs because the path that the Protocol Endpoint (PE) LUN is using is not VVol capable.
A Protocol Endpoint (PE) must be exposed from a storage array prior to registering the Vendor Provider (VP) through the VMware vSphere APIs for Storage Awareness (VASA).
Virtual Volumes (VVols) operations requires specific driver support, and paths to a VVol PE LUN that are presented to a driver that is not VVol-capable cannot be used and are dropped.
Newly discovered LUNs can be independently recognized as PEs from their SCSI INQUIRY data, (SCSI VPD Page 0x86 Inquiry with LU_CONG bit set, indicating that this Logical Unit is part of a conglomerate, and that SPC3 or greater (ansi 0x5) support is advertised ). However, vSphere checks if the driver for the adapter through which the PE LUN was presented is VVol-capable before claiming the path for possible use.
If a newly discovered LUN is recognized as a PE LUN but the path is not VVol capable, the path is dropped instead.
Note: Third party customized images may contain a vSphere 6.0.x compatible drivers but it may not be VVol capable.