It sounds like you need to check the app permissions, to do this:
- On your phone, go to Settings > Apps
- Tap on the Hypnosis Downloads app
- Scroll down and find 'Permissions':
- If this is set to 'Storage', the permission setting is correct so please try deleting the app then reinstalling it.
- If this is set to 'No permissions allowed', tap on it and you should see a section that says Storage - switch that so it is on (as shown below).
- Once you've changed that storage setting, try reopening the app and downloading items. If it still isn't working, please try deleting the app then reinstalling it.