Arc collector: cannot enable offline mode for map

Arc collector: cannot enable offline mode for map

I am trying to setup arc collector for offline data collection in remote areas. I have followed steps from a few ESRI tutorials.
Problem: when I try to "enable offline mode" for the web map within Arc Online I get a pop-up message that says, "This web map cannot be enabled for offline uses..." (My Content > web map details > edit). 
Background: In ArcMap, I created a file geodatabase with domains. I then exported separate polygon, point, and line features to the gdb (features had been previously created). I published the map as a service, changed the capabilities to Feature Access and checked "Create, Update, Sync, and Delete". The map published successfully with a couple "Medium" warnings but zero errors.
Within Arc Online, the features and the web map both say sync is enabled but, again, I am not able to enable offline mode, which is the difference between using collector or not for data collection (given our remote surveys). 
What else could be preventing me from enabling offline mode?

Solutions/Answers:

Answer 1:

Turns out my problem was that the web map was synced and within My Content on Arc Online but I had not shared it with any groups. I did not think I needed to share it unless I wanted to share the map with someone. But, once I shared it with my work group, the map was automatically enabled for offline use and now can be downloaded to the tablet. Fantastic. I don’t really understand why this is a requirement, but I’m not complaining about such a simple fix.

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