I purchased Parallels Desktop 9 for Mac and activated within the Tech Guarantee 2014, however have not received my no-charge upgrade key for Parallels Desktop 10.
You did not allow sufficient time for the key to be delivered or the email with the key got to a spam/junk email folder.
Customers who purchased and activated a copy of Parallels Desktop 9 for Mac from the Parallels Online Store or an authorized reseller on or after August 1, 2014 through October 15, 2014, are eligible for an upgrade to the next version of Parallels Desktop for Mac at no charge, subject to certain conditions.
The upgrade key will be sent to the email that was used during the registration process when you installed Parallels Desktop 9 for Mac. Please allow up to 7 business days for your key to be delivered.
If 7 business days have passed and you have not received your upgrade key yet, you may check your Parallels account, as your upgrade key for Parallels Desktop 10 will be automatically registered there. Log in at https://account.parallels.com/ and select Parallels Desktop in the menu on top. You will see all the license keys registered under your account, including the key for Parallels Desktop 10.