Upon first start-up of CommCare or upon installation, the CommCare app will validate that all of the multimedia files that the application needs to use are present on the phone.
If they are not present then there will be an error message and you will be prompted to install the missing multimedia files.
If you are testing an application without all of the multimedia files and do not want to encounter the error message, you can skip multimedia validation.
You can simply turn off multimedia validation by going to your Application Settings -> General Settings -> Multimedia Validation = No Validation
You must then make a new version of the app and install the new version.
It is possible to manually skip validation for Feature Phone apps even after you have downloaded the jar and jad files.