I have been assisting one of our GIS staff members with a strange Survey123 issue. He has the survey published and shared, and it loads in the browser, the mobile app on an Apple tablet, and the phone browser.

However, when the survey is accessed via the mobile app on an iPhone, it's blank:

We have tried using several accounts to access it (screenshots are from an Admin account), verifying group sharing settings are correct, verified that we had the survey set to open in the app, tried changing the sharing settings to Organization and Everyone to see if that made a different. We've refreshed the survey in the app several times, did the whole, log out, log back in thing, even uninstalled and reinstalled the app, and still get the same issue.
Can't find much online about this, the app version seemed to be the biggest potential fix, but no luck. Has anyone run into this, or have any thoughts on what to try next? Thanks in advance!