I have automatic downloads set to on, for app updates but not to mobile data could this be a reason it’s not working. It’s the same on my iPad Air.
TIA BB
If by Mobile Data, you mean Cellular Data, it is supposed to not be set to that, esp. since you have limited cellular data. But I am not sure if you have the iPhone charging while on WiFi as both are required. Perhaps your WiFi is disconnecting due to location of something while you are charging it?