Are you saying he has lost faith in general or accepts the gospel and the Church as social structures?
The Word is the Church and the Word is God, the two can’t be separated.
Some people can accept something without knowing much about it, hence Jesus said my “people die for lack of Knowledge”
I would sit with him and see if he has enough of the right knowledge to make an informed decision, after all there are millions of Christians all believing different things and all reading from the same book!
Most likely it will be his lack of knowledge and I recommend going to Our Blessed Holy Mother for help, a novena or offering before prayer requests is a forgotten custom and it works so well, bring your Mother flowers before you sit with her and she will fix it with Jesus.
The Father from time to time hides from us but our Mother never hides away, so offer her a Rosary and if you can manage a fast or suffering for the request, that will be what she brings to God and God is so pleased with his Daughter that he can’t refuse her anything, She will bring him back for you.
God Bless.