Listed below are some troubleshooting steps to consider when a desired web map is not appearing in Collector for ArcGIS, the following will be necessary to make maps available:
1) A minimum of one Editable feature service layer.
2) A map containing this layer.
3) Ownership or group access to the above Editable Layer Item.
4) Ownership or group access to the above Map Item.
5) Adequate sharing access for any remaining layers in the Map.