The CCS protocol utilizes several pins in the 'main' part of the connector for signaling and adding the DC fast charge only adds two pins to the connector, verses the CHADEMO system which has lots more, and uses what is closer to a low-voltage Ethernet control signal. That signal is an ac carrier imposed on a dc signal line in the range of 20MHz. If the plug does not make good contact with those signal lines, it could cause the system to fail to initialize. It seems the plug chosen for Europe has more of these issues than that selected for the USA and Canada. The J1772 plug has a mechanical button activated latch at the top of the plug, and the weight of the plug tends then to help ensure proper alignment and thus contact. It does not appear that the plug used in Europe has a similar mechanical latch which would allow the weight of the connector to have more impact on keeping everything lined up. As others have said, sometimes, all it takes is to relieve the pressure on the plug slightly for the unit to then communicate properly with the i3, and then, things can proceed correctly. As I understand it, there was a big controversy over what plug to select, and with different local rules, it was a tough sell...I'm not sure you guys got the best option, but it's a done deal for now. The Euro plug spec ended up with internal shutters to protect the high-voltage pins from inadvertent contact. The protocol and interlocks in the EVSE prevent there being any high voltage there at all until the plug is fully inserted, so it seems like a third layer of redundancy, whereas the USA J1772 spec has only two - you can't remove the connector until you press the release button, and that breaks the interlock signal which drops out the high voltage contactor. In the Euro plug, as soon as you pull the plug out, it closes shutters over the pins in addition to breaking the interlocks and thus causing the contactor to open.
2014 i3 BEV, 2021 X5 45e
(The i3 will be sold soon, <17K-miles, interested?)