I tried creating some segments the other day. Two of them worked fine shortly after creation, the third did not seem to register in my rides -- giving all sorts of excuses when I checked using Strava's built-in segment checking tool like not going the right way or something.
It then occurred to me that this may be because the segment ends inside my Privacy Zone, which I thought wouldn't affect me because I do not show my rides publicly (or whatever the name of that setting is called). So I tweaked my Privacy Zone size and location to shift it outside of the segment and viola! It recognized my rides again.
And also after a while, the KOM and some top spots were filled with obvious forgot-to-switch-Strava-off-and-drove-home entries.