There are a few reasons this might happen.  Firstly, if you are losing your connection when your phone sleeps, it’s likely that your battery and or data usage/savings features are enabled on your phone.  If you wish to keep our app running in the background, try going to your phone’s settings and look under both the battery and data settings to allow our app to run in the background. 

Another scenario is that you have set up your downloads to run over wifi only, and you exited the wifi’s coverage.  To change the setting to download over wifi and on your data plan, go to Settings, then Wifi Networks only, then uncheck the box to deactivate this option.

Finally, it’s possible that your Internet service provider is throttling or even blocking the traffic.  This can happen during peak hours or when you have exceeded your data limits.