This behavior could have multiple causes. As stated on the official website, most of the cases, the application isn't working because of the OTG cable. You should check if this is working. If you are sure that this isn't the reason why you can't mount the stick, try to visit the application's page from Google Play. By doing this, you will be able to download from its description the appropriate files that needs to be copied to your stick so the application can read it. Also, check the official site mentioned above for additional information regarding this matter.