Install and Activate Acrobat XI Pro

I have wasted almost a day of work trying to get this application activated.  I recently purchased a copy of Acrobat XI Pro, and installed the program.  I entered the Serial Number in the beginning of the process, as it is labeled on the box the installation CD was in.  I assumed the installation was successful, until I opened the application and was prompted to again provide my serial number.  I entered it again, and received a message the serial number was invalid, and that I was not connected to the internet.  I found that hard to believe, because I was on the internet.  I followed the prompts to get a machine-code request, which took me to an Adobe web site.  I copied and pasted the machine code and entered my serial number again to get a response code. Only to be told, the serial number is invalid.

I have installed and uninstalled XI numerous times, followed numerous steps found in several posts in this forum, repaired installations.  All to no avail.  I am attempting to install XI on a new Desktop with Windows 10.  I have a full version install, not an upgrade version.