@stueytheround that's terrible. Sorry you're dealing with that. If you've had to jump start it very often that alone could have done in the wiring.
My scooter just had a problem where I thought the battery was bad because it was screwed in tight and still not delivering power. I took it out and put a multimeter on it to verify it's giving a good 12 volts (it was) then put it back in and suddenly it was fine. Didn't look corroded but scraping up the contacts somehow did the trick.
@Fellixe Yeah tried those things. No joy. It's had a few issues electrically for a while, but this time it seems "terminal" (pun intended).