Hi, To show map in collector app may be you can try this option. when you share as a service
you have to go through several dialog box. Here, you find Feature Access option.
here, check mark on Create, Delete, Query, Sync, Update. and then follow rest of the dialog box. at the end click on publish button. Now, when you connect to portal in my content tab you see web layer. Open feature layer file and then open in Map Viewer and save this file. after that open collector app to collect data.
This post needs a little more information to troubleshoot:
1. What user licence do you have?
2. In the settings of the webmap is it enabled for use in Collector?
3. Are you creating your webmap from services hosted in AGOL or Enterprise? If enterprise, what version are you running?
4. Are there any services in there not supported by collector? Such as a feature layer generated from an uploaded shapefile?
5. And the biggie, is there at least 1 editable feature service in there? Collector and field maps won't show maps without one.
6. Finally, try accessing the web map with Field Maps.