I've been having a time trying to sync an offline map using ArcGIS Collector 10.2.7 for the past couple days, using an Android Trimble Juno T41/5.
I had previously decided to use hosted features on AGOL for this particular map, which had 13 different feature types to collect. I also used a .TPK for the base map, which worked fine.
Testing the map was successful with a couple features syncing quickly over wifi or mobile networks. Global IDs were added to all feature classes. Archiving was enabled, versioning was turned off. Sharing as a service to 'My Hosted Services' was done with 'Feature Access' enabled, and all operations allowed: Create, Delete, Query, Sync, and Update.
Since I had tested the device myself with a few features and had success with syncing, I deleted those features, re-synced to clear the map, and deployed the device to field staff. Staff came back with 20 features collected and saved, but had not been able to sync. I was not able to sync the device either.
I tried many many things recommended on the forums to remove the data, but nothing worked to get all the features off.
I tried the python route described here and had a few features successfully extracted: Offline works in ios but not android
Going back to basics finally worked for me:
1. From Data Management Tools>Distributed Geodatabase>Export XML Workspace Document
2. Ensure you are choosing to export the data, not just the schema
3. Then in the same toolbox, use the Import XML Workspace Document tool and voila!!
Perhaps this will help others. Definitely a lot of bugs still out there with AGCollector, even while using hosted services.