Hello @GilP81 ,
Without being able to look at the file in question, we won't be able to provide much insight. When you're able, please send an email to social_support(at)constantcontact(dot)com with your account username, a reference to this conversation (such as the URL or copy-pasted text), and the contact list you attempted to import. Otherwise you can call our general support for live troubleshooting and assistance.
... View more