Your Domain Key is not valid. You can obtain a new Domain Key as follows:
Please find the following section in your web.config file and enter the correct value for DomainRegistrationKey.
<appSettings> ... <add key="DomainRegistrationKey" value="[Enter your Domain Key here]" /> ... </appSettings>
VevoCart Premium Ver. 6.4.0 Assembly version: 6.4.0.7