I am working on a project where we are updating offline basemaps every week to keep them current with locations of where data has previously been collected (so people do not collect the same sites). Originally we had a .tpk file of the study area and this week I released my first update as an .mmpk. I am placed the .mmpk file in the "media" folder of the project and deleted the old .tpk file. However, when users update and use the survey in the field the old .tpk file still shows up as an option.
I worry that the survey will become huge on people's devices if they are unable to get rid of these old offline map files. Is there something that I need to do on my end, or do they need to do something on their devices?
Have you tried getting the users to delete the survey first and download again, this should remove all files associated with the survey. Doing an update just updates the files in the My Surveys folder.
Another thing to try, as well as clearing the app cache suggested by others, is to uninstall and reinstall the app, and then download the survey again.
The problem is likely related to the fact you changed from tpk to mmpk, but now if you continue to only update the mmpk with the same exact filename, this should work with just normal survey updates.