Can't activate Toolbox with my Parallels Desktop for Mac v18 Key

On the "Activate Parallels Toolbox" screen I get the message, "The license server doesn't accept your product license."
It says below that, "You can also use a Parallels Desktop subscription key or an activation key for Parallels Desktop v14 or later."
I am using the license key for my Parallels Desktop for Mac v18 key. Why won't it activate Toolbox?

 

Greetings JamieD3,
Thank you for posting on Parallels Forum.
As we can see, you already contacted Parallels Support via ticket - 4101068.
Please check your inbox. Looks like the wrong key was used upon trying to activate Parallels Toolbox.
If the issue still persists, let us know.
Wishing you a great week ahead!