Gr88, sometimes girls will cancel a date if they are in a bad mood, having bad PMS, or just feel a bit sick. Nothing against you. But they don't want to waste your time or money if they think they will be a "bad date". So they cancel. (Yes, some girls have told me this. I'm not assuming things here.)
Don't take it personally. Ask for another date. If they keep canceling, that's a sign she's not interested. If only girls would say "I'm no longer interested. Nothing personal. Sorry." I've had dates where we "clicked" immediately, we had major chemistry. Some of my dates were very nice, very cute, but...no chemistry. NOW i understand when girls talk about "chemistry". I mean this one girl was the cutest little redhead, very perky, great smile, drank like a fish, funny, but...no chemistry with us.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)