Specific Lead(s) or Contact(s) are not being added to a list in Salesforce

Is the the Lead/Contact Owner "active"? You can check this by going to Setup | Administration/Manage Users | Users. 

 - Is it a valid email? .co instead of .com, etc?

 - Is there more than one email address attached to the contact?

 - Is the Do Not Email box checked?

 - Do you have CRUD (create, read, update, delete) access to the Leads/Contacts? 
 

 
In Salesforce go to

Setup |  Personal Information | My Personal Information

Here look at (for Enterprise and Unlimited editions) and click on the link for your Profile. This will take you to the Profile settings. Scroll to the very bottom of this page and look at your "Custom Object Permissions". You should see that both "VR Email History Contact" and VR Email History Lead" have Read, Create, Edit and Delete permission enabled.

If not, the user will only be able to create a list for leads/contacts they own. The Salesforce Admin will need to change these settings for your Profile. If using Professional Edition, Profiles cannot be changed, a "standard user" can only work with leads/contacts they own. Other profiles may have this same restriction; an admin will always have access to all leads/contacts.