I've attached the Survey project in a zip file (including the extensions folder), if that would be helpful to troubleshoot.
Yes, it is possible to use custom JS function whilst offline, provide the user is signed in (need to be signed in before going offline).
We had some issues with 3.9 and earlier with users being unexpectedly signed out when going into areas of poor coverage or restarting the app between being online and offline. These issues have been addressed in 3.10, which will be released soon, so you should see custom JS functions working offline provided they are signed in at least once before going offline. Also, custom JS functions are not fully supported in the field app and web app in 3.10.
Hi @Philip-Wilson ,