This regards the e9x series I don't know if it effects the others.

So from what I understand they used a down counter in software that is set to 29 or 39 after that many oil changes the reminder cannot be reset. I have seen some threads where people tried to us tool32 to change the Intervals for the reminder and even try to reset the down counter but these don't seem to be effective. Any further info on how to make it work again. Apparently BMW has a TSB that disables it when this happens they don't or can't fix it.