Why is it so hard to date people?

So a while ago a girl messaged me on Instagram and we kind of talked a little. She’s no where near me but I figured we could just get to know a little more about each other. Now she always messages me asking me what’s up and everything. But then when I message her back she responds like we never even talked before. I mean I want chat with her but things always feel so awkward and I don’t know what to talk about. Like I said she usually messages me first but then acts like she never sent me anything.