2012 car sold, apparently not rereported, now claim of insurance

Hi guys! I just got a little problem. In April 2012 I sold a BMW registered in my name. We signed an ordinary purchase contract in which the buyer agreed to re-register the vehicle immediately. Today came a letter from the insurance company at the time, which says: Quote: Dear Mr. Simba, your car insurance was due to an unsuccessful order for payment (I never got anything) w I have to admit that I had not taken care of the insurance at the time. I have often moved in the year and had other things in mind. How should I proceed now? Is the buyer of my BMW obliged to take over the payment? After all, this was not the case. vehicle in the period in question his property and he even used it beyond the 10.07.12. Thank you and greeting Simba