New metal roof over old Asphalt shingle roof

I had a new metal roof installed a year ago in January 2019.
I had a leak in my roof before he installed the new roof. I asked him if he repaired the leak. He said he did not need to that he put a new roof over it. I thought that was an odd answer. But he is a professional and knows what he is talking about.
Six months later there was a spot in my bathroom at edge of the wall. And in the hallway a small rim damp around edge of wall by ceiling. About half an inch.
I called him and he came and looked and said no it was the ac unit.
I have a new unit. The new unit is a complete outdoor unit. I did not want it in the attic.
The spot went away. We had no rain. We had a lot of rain and the spot is back. He is supposed to come and check it.
Any advice on what to tell him. And about his response when I asked if they had repaired the roof before putting up new roof?
Please help!!
Thank you,
Cindy

Cindy,

Without seeing what you are seeing (outside and inside) it going to be near impossible to lend an informed guess on it.

That said, there does appear to be a leak from the roof and it would stand to reason that the roofer would be the one that is on the hook for looking at it.