Phone update

Hi,

at the end of June 2015 I bought a new Nokia Lumia 635 (Windows 8.1) in Florida at AT&T. This went along with a new AT&T SIM card and a prepaid plan.

The phone tells me that there is an phone update available. I don't succeed in updating it though it's connected via wifi. I get the message "We are currently unable to check for updates (80072f8f)." I keep trying since days so it can't be a "current" problem.

Any ideas?

Regards,

Stefan