Fire TV Recast Streaming on the Go issues

I got the more expensive Fire TV Recast as it was on sale during Black Friday week. Only one time can I remember being out of wi-fi range and still being able to stream OTA TV. So last month I sent it back to Amazon under warranty services and they said it needed to be replaced. However the 2nd one which was Brand New still would not stream on the go usually giving error code 77-1005. After uninstalling and reinstalling the app. and doing numerous factory resets Amazon had me return this 2nd Recast. Now I have the 3rd one, again Brand New but the problem remains: Cannot connect to Fire TV Recast when out of router wi-fi range. Now I have LG K20 Plus phone with unlimited 4G LTE from Metro PCS, now T-Mobile. I have streamed DirectvNow, IPTV, Kodi, Vudu, Amazon Video, etc. with no problem so please advise what steps I should take to make this Recast stream OTA on the go. I have tried different quality settings, always allow on the go, etc. Still no luck!