Leaking flat roof

[leonardholl]

Hello,
my cabin is installed with a flat rood a year ago. In August, there have been a leak through the light fitting in one of the upstairs bedroom (flat roof) when rains. The leak would happen after some heavy rains.
I have done the repairs two times. I uses a flame touch and some membrane to seal the roof above the light fitting. It leaks after the first repair, so I extended the repair area for the 2nd time. It holds 2 episodes of heavy rains after the 2nd repair.
It is now leaking again. It does not leak immediately when heavy rains. I noticed this time that the roof leaks quite badly even the rain stoped after an episode of heavy rain. I is planning to extend the repair area for the 3rd time but I feel the leak point probably not have been identified.
Any advice and suggestions are much appreciated. Thanks a lot!

[MountainDon]

Is there a slight slope to the roof ot is it real flat and level?

The actual leaking point can often be a few feet away from where the watr shows itself.

If the roof has some slope look uphill. If truly flat there may be one or more ponding spots.

Is the underside of the roof visible, like in an attic or is the underside all covered with the ceiling material?