This priest certainly has a crisis, since, for him (and all priests) the time of discernment is long past!
The years in the Seminary is the time for discernment. That ends when he accepts his bishop’s invitation to be ordained.
If God was calling him to the vocation of marriage, once he is ordained a priest that then becomes his vocation, regardless of what God was calling him to before. We can make errors in our discernment, but once the decision is made, whatever we have chosen then becomes our vocation.
What this priest needs is to accept that, now that he is a priest, he needs to stop thinking “what if I made the wrong decision” and dedicate himself totally to being a priest. This is his path to holiness.