Traded in old Mac, unable activate license on a new one: "License has reached its activation limit"

I recently traded in an old MacBook for a new one and renewed my Parallels toolbox license earlier today, however I receive following error when I try to activate it on the new Mac:

This license has reached its activation limit. The license has been used to activate Parallels Toolbox on 3 different Macs. To activate Parallels Toolbox on this Mac, you must purchase an additional license.​

I was unaware I needed to deactivate my license on the old mac and am now unable to do so. Also, I currently own just 2 Macs, including the new one on which I can't activate Toolbox, so I should have at least 1 if not 2 activations available.

Is there any means of deactivating my license on machines I don't longer own? If not, I will be cancelling my renewal and requesting a refund.

Thank you.

 

Can Someone help me reset my limit? I just switched to a new Mac and need to use Parallels it tells me that that I have reached activation limit.