I'm saving the Arc Map the same way I always have by opening the map online, save as-> map to create a web map. This usually allows me to use the web map on the collector app, but it's not displaying.
You need to have at least 1 editable feature layer in your map. I would go through the map and check if:
Another thing to potentially check is that if you sign into Collector using a different account than the one used to author the map and the feature layer/feature service that the map and services are shared in a group that the Collector user has access to.
Hope this helps!
I had a problem where a web map couldn't be brought into Collector. It turned out to be that I had used the ArcGIS Online Assistant to change the URL of one of the services used in the map. I had to remove that layer and add it in manually to make the map loadable in Collector.