I thought I figured the process out after I managed to upload a test pic to the sandbox.

Subsequent efforts to upload pix have failed, one after the other.  :-(

When I choose the pic I want to upload, and then click the upload button, it says it is uploading, but nothing happens, even when I give it extra time, 5 minutes or more.

What's happening? All the pix I have chosen were within the size parameters, so that shouldn't be the issue.