Thank you for bringing this issue to our attention. I'm not seeing any widespread reports of issues with our contact servers today, but we can see what's going on. For account and contact security, we'll need you to email us the username of the account you're working on, as well as the name of the list you're trying to add your contacts to, and prefferably an attachment with the sheet that you're trying to upload. Please just send that information to social_support(at)constantcontact(dot)com with a reference to this post, and we'll be happy to look into the issue further.
Aaron H Community & Social Media Support
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