Rejection can bring an urge to explain, persuade or seek one more conversation. The wish for clarity is understandable; the other person still gets to decide whether they want contact or a relationship.
Accept the boundary
If someone says no or asks for space, do not keep contacting them, involve friends to pressure them, or show up uninvited. Respect means taking their words seriously even when you are disappointed.
Take care of the hurt elsewhere
Talk with a trusted friend, write down what you wish you could say without sending it, or choose a temporary break from reminders. Your feelings deserve care; the person who rejected you is not required to provide that care.
Let the future be open
You may not get a complete explanation. That can be painful, but you can move forward without deciding that either person is cruel or defective. A no is a relationship boundary, not a challenge to overcome.