The most common common sources of failure of chargers, particularly cheap Chinese ones, are often easy to fix if you can do some soldering.
If the charger is completely dead, check for a blown fuse (the line=in fuse is usually soldered to the board) or a burned out NTC inrush suppressor. The inrush suppressor looks like a ceramic capacitor but is dark-colored and connected to the AC line-in.
If those check out ok, check the input-rectifier filter capacitor - it's the biggest (aluminum electrolytic type) on the board - sometimes a pair of them. Any bulging or leaking means they are bad - the top (often under a plastic cover) should be flat.
BTW, VERY IMPORTANT! Check them with a voltmeter and make sure they are discharged before you touch anything. These can have 180-360 volts when fully charged.
Replace them with a high quality (non Chinese) capacitor - of higher value if they can be physically fit on the board.
I have put about 80% of the cheap 8A chargers that came with e-max scooters sent to me back into reliable service by fixing the two above things.
If it's non of those things, it could be the a lot of other things - input and output rectifier diodes, switching FET(s), PWM driver, opto-isolator, transformer (very rare) charger logic - but failure of most of these things are much less common.
