I can put them into pairing mode (5x OFF/ON, bulb flashes for confirmation) but hubitat will not see the bulb, have tried using add device before and after putting bulb into pairing mode.
An update for anyone finding this later. I had the GU10 inside a fitting which was a thick metal tube, I was able to pair by removing the bulb from the fitting.
Vesternet offered to refund the bulbs I purchased which was excellent customer service, I'm glad I found the issue before returning the bulbs.