Your specific issue was answered by David in your other thread, but I'll reiterate it here as well.
Your issue is due to your contact already receiving the Autoresponder campaign previously. In order to not "spam" your contacts our system recognizes that your contact has already received the email campaign on that specific autoresponder series and so when you add them back to the series the system will not send out the same campaign.
For the full answer please refer to your original thread. https://community.constantcontact.com/t5/Developer-Support-ask-questions/Adding-Removing-Contacts-and-Sending-Emails/m-p/311945
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