having just replaced the TCU on my 04 x5, I think its possible that once BMW assist is disabled because it expires, the TCU somehow gets 'turned off'. Perhaps its looking for a specific connection it no longer has. I say this because I had a similar experiance where SOS and assist didnt work. I took the car to the dealer for something else and on a sheet they printed I saw 'assist' disabled. as soon as I swapped in a newer unit, it fired right up and I am chatting away.