This happens to me a lot. There's mutual attraction, yet no replies. Some times, I even try to setup a job-related meetup; smoothly/secretly, it's a actuallly a date, but still no luck.
These are girls that are actively hovering around me; voluntarily offering their digits; giving stares and looks; checking up on me when I talk to other girls. So I have good suspicion.
Maybe ask a couple of questions before coming to that conclusion.