When you download the Agent installer (.msi) file, you are provided at the same time with a customer key that is specific to your account. You will need to enter your customer key during the installation process. If the customer key is not recognized by the installer, the installation will fail with an error message telling you that "The Cloudamize server failed to validate your customer key."
To resolve the error, double-check that you have entered the correct customer key. If you confirm that you are using key that was provided, and yet you continue to receive this error, open a BitTitan support ticket. See How do I get support for your products?