Do you have a backup of the vCenter DB before doing the upgrade on the secondary, the one you took at step 4 on the Secondary?
You need to restore this DB and vCenter will start on the Primary and then upgrade it to 5.1 U1.
Do you have a backup of the vCenter DB before doing the upgrade on the secondary, the one you took at step 4 on the Secondary?
You need to restore this DB and vCenter will start on the Primary and then upgrade it to 5.1 U1.