Newly built ESXi 6 hosts will not detect LUNs zoned to them. The storage is NetAPP FAS8000 series FC. After multiple scanning and refreshing, nothing changed. The storage guys said they got everything right at their end.
I found this VMware KB which says RSCN event be enabled on the switch in order for the host to detect LUNs after a zone change without reboot. I shared it with the Storage guys and they agreed to check it later.
Meanwhile, I rebooted the hosts after which all hosts detected the LUNs. Additional LUNs were added and detected after a rescan. The storage guys said they didn’t change anything at their end though.