I ran into this problem less than a month ago with the exact same light. Except I was provided with a known dead power supply.
Back in the day I used to repair computers so I’m pretty familiar with small electronics and I also remembered that most older laptop power supplies are 19 V 4.62 amps 90 W. That is exactly the same Voltage output of the Kessil PS. I grabbed an old Dell power supply checked it with a meter. I was good to go so I cut the end off Dell PS because it was too big for the Kessil. I put the Kessil end on the Dell PS and it works like a charm.
Obviously, please don’t mess with wiring if you’re not sure about what you’re doing. Unplug everything and move it away from the aquarium and to a workbench.