I too am having this issue. Clicking the “Load” button does not open the native files app. It only opens a folder for content created in ExpressMix or that was somehow already in it’s own library.
On the other hand, WavePad works perfectly; click on File> Open File From Device, and it loads the native files app and I can access all my samples and loops anywhere.
Can someone please fix this? Or tell me what I’m doing wrong.