I wanted a map for offline use in Survey123 that included a polygon layer for reference. I created an mmpk and linked it to Survey123 using this process: https://help.cadasta.org/docs/kb/arcgis-pro/create-an-offline-map-with-feature-layers-and-link-with-survey-123/
I had to download the map to my computer and upload it to my ArcGIS Online organizational account manually (using add new item) because I kept getting an error that I didn't have space in my account when I tried to upload directly to ArcGIS Online. I think that is due to the 10MB upload limit, since I have plenty of space in my account. Once I successfully uploaded the mmpk, I was able to link it to my Survey123 form.
When I download the offline map in the Survey123 app I can see the polygon layer in the thumbnail, but when I open the map in a geopoint question on the form I can see the offline basemap but not the layer. I checked the projection and both the basemap and the polygon layer are using wkid 3857 as their projected coordinate system. Its not a scale visibility issue, since zooming in and out does not make the layer appear.
The resulting file is 22.9 MB, so I cannot attach it here unfortunately.
Any ideas on how to fix this are much appreciated!