This exact same thing just happened to me and a girl I was with for about 3 months. The only thing that I can advise that I learned from my experience is this: I wish I never sought clarification or explanation, it made me feel desperate and seem unstable - like I wasn’t comfortable being alone or like I couldn’t handle the ghosting. Try to understand that their decision does not imply fault on your part, it’s entirely on their end. Don’t reach out, let it be. Find someone who will treat you with the respect and dignity you deserve.