Cannot fill PDFs in Acrobat Reader mobile app even though security allows for filling in form fields

I recently added security settings to some PDFs to prevent editing and commenting; we only want them to be able to fill the fields. (There are no signatures on these documents so signing is not required.) For some reason users can no longer fill them out in the Acrobat Reader iOS mobile app. The fields no longer appear blue and the following message appears:

These forms worked fine when there was no security applied to them. Users also have no issues filling the same forms out on the desktop app for Acrobat Reader DC and Acrobat DC.

These are the current permissions under the password security settings:
Printing Allowed: High Resolution
Changes Allowed: Filling in form fields and signing existing signature fields
Compatibility: Acrobat 7.0 and later

I also tried broadening the permissions and decreasing the compatability, however the fields could still not be filled:
Printing Allowed: High Resolution
Changes Allowed: Commenting, filling in form fields, and signing existing signature fields

Compatability: Acrobat 6.0 and later

Is this a bug or are there some additional security settings that I'm missing in order to restrict editing/commenting and enable mobile document-filling?