Cargo door won't open
 

I have a 2016 Express that is a company vehicle. I closed the back cargo door on Thursday morning at work and it didn't close right. I grabbed the handle to try again and ......nothing. It feels like the door is locked. The key and the manual unlock inside don't do anything. I pulled the inside panels (both panels)and everything is connected like is should be. I can manipulate the lock rod and the rod for opening the door manually inside the door and......nothing. So I'm down to brute force and ignorance.. Any advice would be great. It will go to the shop this week some time but up until that point I would still like to get in the back....even if I have to hold the door close with a rope.

Are those latches still made of plastic? Not too many 03-up have turned up in the junkyards here for me to look over.