Few of our members reported the same issue (6.0 missing older API) that causes Streetpilot to crash on Android 6.0. At this time I don't know of any fix. Perhaps there is compatibility mode setting in 6.0?
We can hope for Google to fix the issue in 6.x or for Asus to update Streetpilot. As soon as Google releases SDK with 6.0, I will try to look in the details of the problem and possible a work around.
Sorry for the bad news.