Is this a intermittent noise? Or just when you move the steering wheel?
Could also be the anti-roll bar.
Remove the licenseplate cover and unscrew the big screws at the rubber sleves.
You need a 16 or 17mm Nut.
Then shake the Twizy a few times form side to side to settle the suspension.
Push the bar all the way up and fasten the screws again.
Some grease or oil on the joints would also be a good idea.