So I'm doing Curtain Call at the Tampico, and I just met Dean after picking up Vera's Partitures. It says once I pick it up that the Backstage Key has been added to my inventory, but once I exit the conversation and head to the door, I cannot enter as the door will not unlock. Has anybody else had this problem?
NOTE: When I check my inventory the Backstage Key does not appear (at least not in the miscellaneous section).

Try reloading to the start of the theater and do it again I guess.

Done that several times brah... btw, playing on 360.

I know, the DLC has only been released on the 360.
Try searching his body again I guess, go to his body, loot it and press the "Take all" button and try to open it.
Other than that I have no idea what went wrong.
Did you take the key at Dean's room and Vera's room?

Whose body? Vera's Partitures are the sheet music in front of the stage of the theater.

I'm having this SAME EXACT issue, and it is pissing me off... logically the "Backstage Key," which is in my inventory, would open the door entitled the "Backstage Door." This is not the case. I have also tried reloading and tried every door in the area (while evading fire to boot), but to no avail.

THESE BUGS ARE ANNOYING ME!

Hey guys

You need to be using the door to their right, which is also labeled “backstage door.”

Hi mate, That key opens the "Backstage" door on your right hand side. You then have to make your way around to confront Dean.

the door on the left of stage will be locked...the door on the right of stage (looking at stage) is for the key.......