I know you are logic-challenged, but stay with me here. First we have the literal one-in-a-billion chance the virus originated naturally in the exact same city as a lab studying this exact same virus. Now China still refuses to cooperate on the origin of the virus.
It's a huge loss of face for them if they admit the virus came from the lab but not nearly as much loss of face if it came naturally. They refuse to cooperate because the true origin would be obvious to everyone. Simple, basic logic and reason.