A "locked" room (worst name IMVU could have called them) is not actually locked, it is instead a room that does not have furniture functionality built into it.

The room was either made prior to furniture availability in IMVU or the mesh maker did not add the proper nodes needed in the skeleton file of the room.

Sometimes this can also happen if the room was placed in the wrong category in the catalog, if that is the case moving it to the rooms category and cleaning cache should fix it.

The only person who can make a locked room unlocked would be the original mesher of the product as you need to have to source files to properly align the furniture nodes that would have to be added to the room's skeleton file (xsf).

If the room is simplistic a room, such as a basic box, another room mesher should be able to experiment and figure out where they go but it would be a very time consuming process. It would probably be faster for them to just make a new room to fit your needs.