Upgrade to Acronis 2015

I purchased 9 licenses (3 family packs) of windows version late 2014. All my computers say they are eligible for a free upgrade to 2015. When I click the button to upgrade, a window pops up that says...

Get ready for Acronis True Image 2014
Here is your upgrade serial number:
xxxxxxxx- (8x8)
Downloading new product, please don't close the window

The window never goes away, and as far as I can tell it does not appear to actually download anything. So, I close the window after 30 minutes and strangely, a new window DOES finally appear with a new serial number. The text immediately following the new serial number is: "The serial number is incorrect"

This is an office building with high speed internet connection and no network/firewall concerns. I ran the update on one computer and it worked great. That PC is now running 2015. But all other 8 machines are still running with their 2014 version with active serial numbers previously purchased in 3 separate family packs.

How come the update only worked on one PC? Why do the other PC's seem to freak out when I attempt to upgrade? Note, the serial number given by Acronis is the same serial number that was given for the 1st PC that DID upgrade successfully. So it would make sense that the serial number is not valid. But why is Acronis giving me the same serial number when I try to upgrade the other 8 machines?

thanks in advance!
Merrill