Leaking fixed skylight
Some of the skylights have a removable trim around the outer perimeter,designed to access the glazing.Check to see if this was refastened securely and any gasket material isn't folded over.
If this is built like the functioning skylights,the screw holes through the aluminum angled caps sometimes get striped and you don't get a good seal.
I just repaired one in the spring where the wind would blow the rain up past the top cap and it would appear to be coming out of the glass.
Another good fix if it only leaks occasionally,say heavy rains,is to install a diverter behind the skylight to move the run off to either side of the unit.
Let us know how you make out.