A friend of mine used to cancel appointments a lot. A common friend of ours got really pissed about having their appointments canceled repetedly, often very late or last minute. Their friendship broke over it, tough it was only the last staw.
Appointments i had with my friend got canceled too a lot. I spoke about it with her and it turned out that she was having mental health issues and just didn't find the curage to be open about it. So we talked it over and now the agreement is that i always treat plans we make as optional. A cancelation is expected and never a big deal, i'll always have a backup plan ready.
I guess what i'm saying is, don't think it nececarily has to be about a person not wanting to meet with you, sometimes they just can't. And that is fine.