Welcome @traitrai. So are you, like, flirting with them and it seems like they’re flirting back but then it’s a no go? That exact thing basically happened to me last week (but with a dude) and it sucked, so I know the feeling.
Flirting can be kinda complicated, some people do it because they’re genuinely interested in the other person and some people don’t take it too seriously. The best way to find out is just to ask them out, like you’ve been doing. When you ask them out, are you just asking them on a date or to be your girlfriend? Also, and I apologise if this comes off a bit blunt, but why not just ask them out right there and then rather than the next time you see them?