Hi Tim,
Thanks for your testing result. The pure cloud user could not access OneDrive for Business iOS, so the issue is not only for the ADFS users, but the cloud users as well. Therefore, for the next step, please follow the instructions below:
1) Have you tried to re-install the app when you tested the pure cloud user account? If not, please have a try to make sure the app was installed correctly. If you can share with us the version screenshot of the OneDrive for Business for iOS, the sharing will be much appreciated.
2) Have you tried to use another network environment to have a test?
3) Please share with us the tenant information, and we could investigate the issue from the back end.
1. The tenant domain information. (E.g. contoso.onmicrosoft.com)
2. The email address of this Admin’s Office 365 account.
3. The contact email address
4. One ADFS problematic account and one pure cloud problematic account
To protect the information, I have sent you a private message with a subject of "Information Request".
a. Please go to the "Your details" section on the right side of the community site.
b. Click "Private messages".
c. Click the subject title of the response to read the message.
d. You can reply by using the form in that display to provide the information requested.
Best Regards,
Andy Sek