Something may have come unplugged inside of the scooter, or your charge fuse may have failed, if it has a charging fuse. If it’s under warranty, I’d reach out to the manufacturer or distributor first, since trying to fix it yourself could void the warranty. If it’s not under warranty, I’d open it up and look for loose/disconnected wires going to/from the battery and charge port. Also look for any in-line fuses. It will be a thick spot at least an inch long in the middle of one of the cables going to the charge port and battery.
I haven’t worked on a City Sport before, but these are my best guesses.