Westfalia tow bar will not attach

[rubberduck182]

Hi all,
I had a detachable towbar fitted a few weeks ago. Been very pleased with it - really easy to attach / detach, until today. It just will not click in to place. I've tried both key positions, wiped the male/female connections but nothing. Every previous time the handle simply spun around to the 'connected' position.
Any tips?
cheers.