If you receive such an e-mail after asking for activation, we believe from our records that you are not the licensed user for the product that you tried to activate. There are many reasons that explain why you have been denied activation, but in general it is because the e-mail address you have used to request activation is not the same as the e-mail address of the last person to activate that product.
This might be because:
You have inadvertently used another developer's product key to attempt activation
Yes, this is quite common with companies that hold many licenses--we find that some companies are particularly bad at maintaining their digital assets and license assignments.
Your e-mail address has changed, for instance because your company name and domain has changed
Again, this is quite common. Companies get bought and sold and change their name with rebranding. We have no interest in and do not track company history of each purchaser and, as such, we do not unilaterally change our records regarding licenses.
You used a personal e-mail address to attempt activation of a product at home
If you wish to activate your home PC, please do this by sending an e-mail from your corporate e-mail account rather than your personal e-mail account.