That error code was common in the Windows 8 -- W8.1 update... many people tried to update at the same time and servers just couldn't handle that much traffic.
First you can try the SFC /SCANNOW method to repair any problem, also you have the Automatic repair option and Refresh the PC without affecting your files.
If none of that works, you can try downloading the ISO file of W10 as last resort. Another option could be waiting some days and see if the update option shows again.
07-29-2015 02:51 PM