It will depend on the reason why your ex is doing no contact. If he exercises no contact to heal and recover, and move on then there is no chance of reuniting with him. If his intention is to get back with you then there is a chance of getting back together.
It's difficult to know why a person is doing no contact. It will become a deadlock when the person doesn't want to get back with you.
You will have to wait for more than a month to contact them because the majority of them employ no contact for a month. By then, you will know whether you're a lucky one or not.
When your ex contacts you when you're doing no contact, it's better to break the rule and receive the call or reply to his text. If you don't receive his call or reply back you'll lose the chance of ever reuniting.