Flash drive not showing my iPad files

Hi guys, I recently brought a San disk wireless flash drive 32gb. I have downloaded the San disk app and have securely connected it etc. When I have the app open I can easily transfer files off of my camera roll but when I want to find files such as movies or my music, I can’t select any files as it says the folder is empty?
Please tell me where I am going wrong here? Many thanks.

This is a limitation of iOS. iOS only gives third party apps access to the photo roll. If you have music or videos stored inside the iOS music or video apps the media drive app will not have access to them. You can connect the WFD to the computer using USB and copy the music and video to the WFD then the media drive app can stream them to an iOS device. 

I’d like to know why none of this is addressed in your advertising. I bought it for music files and other docs. It would have been nice to know…

this is an iOS limitation not the device. this is simply how iOS works.