Hi Olivia,
There may be some concern on his part about the fact that he is a Manager when it comes to the likelihood of approaching you.
However, that may not be the main reason why he hasn’t approached you.
Also, if he is taken, he is most likely not all that into his partner if he is capable of stopping while he is in the middle of opening a door just to stare at you right in the eyes as you walked past.
The root cause of his intense stares may have a lot to do with him trying to figure you out. That may be why he never smiles. He could be contemplating you and what you are all about.
Until he has figured you out, he may continue staring at you intensely for some time. However, when he does figure you out, he may either choose to approach you or decide against it if he feels that he wouldn’t be compatible with you.