Originally Posted by
xooz
When you book a ticket with VN from DL, you likely have a second PNR with a completely different 6 character "record locator" that was created by the VN reservation system. When you go to VN's website, it is expecting the VN PNR ID, not the DL one. The VN record locator is in the Delta PNR somewhere. You could call DL and ask.
OP stated he called DL to get the DL PNR.