My Lumia 640 XL will not update

It is running version 586.36 and when I tap the Phone Update I get a grey bar across the screen and nothing happens.

It has plenty of juice. Fully charged and connected to power supply.

Phone seems to be working fine other than that.

Any suggestions?

Could be the server issue. I just updated mine to 586.71.. Try again later?

I've tried it several times during the last few days, including 2 minutes ago.

Touch " Phone Update " and I get the grey bar and nothing else.