When someone is mad at you....

And you genuinely apologized and that didn't fix anything and you tried to ask why they are so upset (because it appears really irrational) and their only response is to say they don't know how to explain it and they leave it at that. Move on from them? I've tried to fix things and this person obviously didn't want me in their life to begin with if they are choosing to hold a grudge when we were semi close for 3 years.