I had this same problem after updating my moto g on virgin mobile to marshmallow. I was able to get out of that screen and access stuff but couldn't make phone calls. I booted in safe mode, cleared my cache and everything else people did in this thread. None of those things worked obviously. Finally i went to settings ->system update and updated every item in there. .. prl, profile. .. then i got a brief message about a SIM card error. Was still stuck on the screen and it was toggling between trying to connect and DDR message. Turned off my wifi and turned on cellular data. Then it downloaded whatever it needed to and started working fine. I am now able to make calls and do not have that activation screen anymore. So I'm not claiming any sort of concrete solution but something in there has to be a clue.
The only solution I have found for this is to install go launcher from google play, another solution will be to install the original ROM that is android 5.1 that I imagine it also solves it I hope that it has been of help
Daud live in USA. Not sure of the moto g version it was my mother in laws. I think it's from 2015. Also the download only worked with cell data turned on.
It most definitely has to do with not being connected to a plan. The people who have solved the problem downloaded the fix/update over cellular data, and who still have the problem seem to not have a plan attached to their phones. Like I said before, I think it's an issue with the carrier, but without having a plan, they're probably not very likely to be of much assistance. That's been my experience at least.
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