Cannot Backup Lumia 640 - Microsoft Community

once in blue moon notification phone has not been backed while, though backup on. when click on "back now" operation goes 96% , stops, saying:

"we can't connect onedrive -- update phone , try again"

phone runs 8.1 -- connecting onedrive backup require updating phone????????

anyway, tried several times update phone 8.1 10, upgrade advisor says:

"the windows 10 upgrade isn't available phone right now. we're trying determine if phone can support windows 10. "

which, of course, can. makes no sense.

what heck going on?

i aware of explanation, need make sure.

1. once in while prompts because "there has been no backup while?" them too?

2. when login onedrive site don't see backup in onedrive -- no files or folders -- empty. should see if backup worked?

1. yes

2. go onedrive > cogwheel > options > device backups

there see this:

Mobile Devices / Microsoft Lumia and Nokia Lumia / Software update