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.
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, were eligible for an upgrade to the next version of Parallels Desktop for Mac at no charge, subject to certain conditions.
An upgrade key for Parallels Desktop 10 was sent to the email used for registration of Parallels Desktop 9 for Mac.
If you have not received your upgrade key, you may check your spam/junk email folder or your Parallels account, as your upgrade key for Parallels Desktop 10 was automatically registered there when issued.
Log in at https://account.parallels.com/ and select Parallels Desktop in the menu on top. If required, switch to Licenses tab. You will see all the license keys registered under your account, including the key for Parallels Desktop 10.