Hello,
I am having the exact same problem. I am running the UnityVSA v4.0.1 with ESXi 6.0U2. I have iSCSI LUNs working great. I followed all of the VVOL configuration steps documented by EMC and VMware. My VASA provider for Unity looks great in the Web Client, but I see no Protocol Endpoints showing up in the vSphere Web Client. (PE's show up perfectly on the Unity side.) SSH output is the same as yours with "syncError" for the "Status":
[root@labXXXesx301:~] esxcli storage vvol vasaprovider list
emc-unity.XXX.lab
VP Name: emc-unity.XXX.lab
URL: https://emc-unity.XXX.lab:8443/vasa/version.xml
Status: syncError
Arrays:
Array Id: EMC:VIRT1619XYV9HW
Is Active: true
Priority: 0
Our vCenter is running Windows Server 2012 R2, and we are using an external PSC, also running Windows Server 2012 R2. I checked the usual troubleshooting steps -- NTP is syncing time identically across hosts and the UnityVSA. Also, the UnityVSA is only registered to (1) of our (3) vCenters. Our vCenters are in "Enhanced Linked Mode" so they all show up in the Web Client, but only one of them is showing the UnityVSA VASA provider, which is good.
I also tried to update the certificate using the "Refresh the certificate" option in the Web Client. This gave me a certificate valid for 365 days, but that doesn't seem to help. I've tried numerous "Rescan" and "Synchronize" options for the VASA provider, and also rebooted the vCenter, but the "syncError" message seems to persist, and the Protocol Endpoints do not show up.... and vVol datastore remains read-only.
Anyone else able to get vVols to work on Unity with iSCSI???