Active job

Outside room leaking corner

I need some options to try and sort this. Only one corner of this outside room (stand alone) leaks. It is the most exposed corner, and rain can drive into there on occasion (only ever noted in winter-past 2 or 3 yrs only). I have tried simple window sealant as pictured but problem not totally fixed. Water only noted at the bottom, somehow thru edge of door. Nil ceiling/other leaks. NB: It has been electrically certified + is powered.