Hard to tell what that picture is even showing, it's confusing to me because of what looks like a piece of wood paneling on the left side.
It may just be the way the picture was taken.
If that's just a wall and that a glass shower door it's looks more like someone's not been closing the door tight when taking a shower.
The only seam in that area that could leak is around that door frame.
You should have used silicone caulk after cleaning the area of old caulking and wiping it down with rubbing alcohol.
The tub has a lip on the sides that's about an inch high and the encloshure sits over that so there's about a 0 % chance that it's leaking. In fact most often no caulking is used at the bottom when installing an encloshure.
Also make sure no one caulked over the drain holes in the bottom track for the door. Even the back side where the two pieces of the track and side rail go should not be caulked, there has to be a way for the water to drain back into the tub.