Hi thanks for your input.
The actual message on the screen is " tow bar not locked".
I've just tried holding the button but that still hasn't fixed it.
It does try and move and there are no grinding or grating noises but it doesn't come out.
Does that suggest the AHK module needs to be replaced?
The guy that has been working on it for me is convinced that the hall sensor is where the problem lies?
Another update to further the knowledge of these swivel tow bars.
It turns out the root cause of all my problems with the tow bar were water that had gathered in the right side of the boot as the result of a grommet letting water in. Several copper communications wires became badly corroded and amongst other erroneous warnings the tow bar gave a "tow bar electrics" warning which I regrettably ignored and went instead for the cog replacement option. As I said in my earlier post the cogs turned out to be fine so I have one available if anyone needs one. After having all of the corroded wires replaced and several coding corrections carried out to undo the erroneous warnings affecting other things such as lights and adaptive drive, I still have a tow bar that will not function properley. We can get it to pop out and to pop back by short circuiting the system. We can get it to pop out and stay out so we know the motor is fine. The problem now is that the tow bar appears to need re-initialising and neither BMW or any tow bar specialists are able to do that apparently because they don't have the software. I also get nine bongs and the warning symbol on start up which we simply cannot get rid of and which is very annoying.
I have had contact with over a dozen westaflia agents who are unable to help me willing though they were. And BMW main dealers as always just want to replace the lot at somewhere around £1800.
If I replace the working tow bar with another either new or used I cannot be certain that it will be initialised and integrate happily with the cars control module and cas system. I can park the tow ball in the out position which is some use but I can't get rid of the warnings.
If I could get hold of a used one off say a front end crash damaged car replacement would be worth a try.
It is most unsatisfactory that a perfectly good mechanically functioning tow bar can't be used because of a coding/sensor blocking.
I haven't given up yet but I'm running out of options.
I have the same on mine. I did come across a post on a US forum about a non return valve/ plunger type assembly in the top of the tank which gets gummed up and sticks resulting in water siphoning out of the overflow although haven't had time to investigate.