On my iphone I can see the map in the download map section and I can download it. Once it finishes I do not see it in the location geopoint selection. It does work in the desktop version. Why is it not displaying on my iphone
Can you please share some more information about the version of Survey123 Connect and App you are using, also the iPhone model and iOS version?
What sort of offline basemap are you using and how did you create it, is it a tpk? Have you tried following the steps outlined here: Prepare basemaps for offline use—Survey123 for ArcGIS | ArcGIS
If you are still having issues can you please send a copy of the survey and offline basemap you are trying to use so we can investigate further?
Check the file size that it's showing on your phone and compare to the version on your PC (and tje item size on ArcGIS Online if you have access). If the tilepack doesn't finish downloading to your device, the item will show up in your Map list, but you won't be able to open it. And you won't get any sort of error message if the download terminates prematurely for some reason.
From experience, downloading a tilepack is a bit delicate-- you shouldn't try to do anything else on your device while it's happening, and also try not to let your device go to the lock screen-- I suggest keeping it on your desk in front of you and tapping the screen when it dims before the screen locks.