I've created a map in arcgis online and followed multiple instructional articles on how to share a map on/with collector but nothing is showing up in collector. I should mention I'm on the free trial but don't think that's the issue. Any help would be appreciated. Thanks!
I also had this problem, and after a whole bunch of persistence I figured it out. When you go through the 'Share As' process in ArcMap, and when you're at the Service Editor window, choose 'Feature Access' and be sure that 'Sync' is checked as one of the Operations allowed.
I also read several tutorial examples, but none of them made this detail very clear. Good luck!