If you try to select a theme for drupe but get it right, try this:
- Make sure you are connected to you 3G network or at that you're connected to wifi.
- Sometimes, downloads may fail because the device's download manager is off. Check its status by following this flow: Android settings > Apps > All > Download Manager. If it's off, turn it on. If it's on, try toggling it off, then reboot the device, toggle it on again - and retry downloading the theme.