This issue only needs to be tested in 1 device. In web as admin, go to Site administration > Mobile app > Mobile features. In "File type exclusion list", add two common file types, e.g. PDF and PNG. In a course, add 2 file resources if there aren't already, one for each type of file configured in step 2. For images/videos/audios, make sure you configure Display=Open in Appearance when creating the resources. In the app, login as a student and open the course from the previous step. Open the first resource and click "Open". Check that you see a warning saying that the file may not work in the app, and you see a "Don't show again" checkbox. Confirm to open the file without marking the checkbox. Check that the file is opened. Click to open the file again, check that the warning is displayed again. Now mark "Don't show again" and confirm to open the file. Check that the file is opened. Click to open the file again, check that the file is opened with no warning now. Now open the other resource and click "Open". Check that you see the warning saying that the file may not work in the app (the don't show again is applied for each type of file).