Thanks, Randy, for the tips. I double-checked and there are 2 feature layers that are editable (sync, upload, edit, query, create, delete) in the Collector Map.
I also made sure in the ArcGIS Online map that these 2 layers are enabled for editing.
But when I try to download my basemap in Collector, I'm still getting the same error: "Map Download Failed. A layer does not have the correct editing capabilities. The operation could not be completed. (AppFramework error 9)."
Any other suggestions on how to resolve are much appreciated! My goal is to be able to download a basemap so I can collect field data offline (some of the fieldwork is out of the reach of a signal).
Thanks!!