Hi Char,
Try talking to him face to face.
Whatever the issue may be, there is a possibility that it could get resolved if you both have an honest conversation with each other.
It’s best to avoid getting emotional or talking too much during the face to face meeting. Let him do most of the talking at first.
The idea is to give him an open floor to express his grievances or what may be bothering him.
This approach gives the both of you a much greater shot at coming up with solutions as a team.
Being able to do this the right way could help to ultimately get him back.