if they are messaging you, and the write back something that isn't much to reply to, don't reply to it, I suspect this is where you may be going wrong. saying good bye to them and all that.
Prime recent example for me is banged this MILF one night then messaged her a few days later saying, the other night was good, we should catch up again some time.
her reply was I'm sure I will see you around.
I replied with haha shut down, no worries take it easy (think this is the part that worked)
the next friday she was saying hey want to have a cheeky catch up.
BAM tapped that numerous times and yeh...
I'm shit at telling stories, you will learn this