This cache is NOT at the posted coords. The posted coords take you past another neat (modern) theater, which feels more like watching a movie in your friend's basement than the typical large theater chains. But you're not here for movies. You're here for caching.
This cache IS the bonus for the Historic Theatres of Birmingham Adventure Lab. You'll need to complete all 5 stages of the lab to obtain final coords. You'll also need to use stealth!
If you haven't already, download the Adventure Lab app, and search the area. You'll be able to locate the stages of this lab, and subsequently take a peek back in time to how Birminghamians used to entertain themselves before TV, (and before streaming, for the Gen Alpha crowd.) Check the journal entries after you've completed the last one, and you'll receive the coords for the cache.
Please watch your surroundings. Those other people aren't extras, and you don't want to be the main character for the day.
As they say in show biz, break a leg!