If your buyers are not being added to your GetResponse account, it may be that your lists are not set up for single optin. To check this and make any necessary changes, log in to your GetResponse account and ensure that it is set for single optin.
Instructions for enabling single optin with your GetResponse account can be found here:
If single optin is set up you will want to double check all of the GetResponse entries within the product editor to ensure everything is correct. If the settings are correct disable the GetResponse API integration and then add your API key again to re-enable permissions.
Manage your GetResponse account form within your JVZoo account by navigating to:
My Account> Integrations> Manage JVZoo GetResponse Account
Manage GetResponse here