Seadoo key or aftermarket? Check the key for magnetism. I have 5 seadoos and 4 had the seadoo key. The one with problems had an aftermarket one. I compared the old seadoo keys magnet to the new junk and it had no magnetism.
The dess post has a reed switch that uses the magnet in the key to complete the circuit.
Also check all fuses for corrosion. My 97 has 2 fuses in the mpem and one in the rear electrical box. Yours being newer may have more.
I'm no seadoo expert but am becoming one as I have 5 of these now that all have small issues that I am working through. I mainly work on motorcycles as a hobby, the seadoo are similar but quite different> lol