Here are some possibilities for why you are having less than ideal conversations:
1. They are tired.
2. They are juggling other PMs.
3. They are busy adulting (chores, at a job, having side conversations with their SO, etc)
4. They understand from experience that when they give an inch, guys tend to take a mile.
5. They aren’t interested in guys but don’t want to bruise your ego.
6. They are playing hard-to-get, designed to test your patience, tact, charm.
7. They field the same questions ALL the time. Answering them gets boring.
8. You didn’t ask for permission to PM and they are annoyed.
9. They just aren’t a very interesting person.
10. They are catfish.
It’s attractive to be interesting and to withhold tickle talk. It feels good to be treated like a person and not like a cheap means-to-an-end, which, like it or not, is how it can come across.