Hi JasonT1, According to our licensing policy, an upgrade to Parallels Desktop 11 for Mac is supported from the following versions only:
Parallels Desktop 9 for Mac
Parallels Desktop 9 for Mac Upgrade
Parallels Desktop 10 for Mac
Parallels Desktop 10 for Mac Upgrade
If your previous version key is for Parallels Desktop 8 or earlier, please visit the Parallels Online Store to purchase a full license for Parallels Desktop 11 for Mac.
Please check your private message and respond, so that we can help you better.