I am having the same issue with Collector and Field Maps. Once I set an offline area, the map will not return to "online" mode. I created adn deleted the offline areas on Friday. In fact, I deleted all the offline areas today and the map will not switch back to "online" mode.
I was able to return to online mode with a new map (same layers - no change in sharing). I'm concerned about pre-generating offline areas now because I don't want to have to keep re-creating my map.