Public charging

I've had my I3 for a few weeks now. It charges at home both on the 3 pin plug and the tethered wall sockets we've installed. It also charges on the rapid chargers which provide their own cables.
My problem is if I try to use the blue cable I got with the car for public charging stations. The only ones I've tried so far are Charge Your Car stations. I can not get my car to charge on these units.
I took my car back to the dealer who have assured me the cable is not faulted and my car is fine.
Am I doing something wrong??

Have you checked the charging setting in the car? I've connected to public chargers using the cable and forgotten to switch the charge setting from "off peak" to "charge immediately" on more than one occasion. You come back to find no charge gained and no obvious reason why. It maybe worth a check.

I have just had an email back from Charge your car. They've informed me the units I'm using have old soft wear and will not be able to provide enough power to charge my car but enough to charge a Nissan Leaf.
Apparently they're due to be replaced. Fingers crossed.