In the autoresponder settings page, under the 'Options' tab you will find a setting 'Action when all messages sent'.  This allows you to choose what happens when your subscriber has completed the message sequence you originally added.

The available choices are:

Set to Finished (the default) - If you add messages to the end of the sequence, the subscriber will not be sent those new messages.
Remain Active - The subscriber will continue to receive new messages as you add them to the end of the sequence.
Change Autoresponder - Change the subscription to a different autoresponder.

Where you added a new message to a 'Finished' autoresponder, that is why your contacts are not being sent the new messages you add.

Even if you change the autoresponder setting to retain the Active status, it will not trigger contacts that already have their status set to Finished, to send the new messages, so to fix this you need to change their subscription status.

The Solution - do this:

  1. Filter your contacts to show only those subscribed to the said autoresponder.
  2. Once the filter is in place, choose ‘Edit matching contacts’ from the ‘I want to…’ drop-down menu.
  3. On the Edit Matching Contacts screen, choose the said autoresponder in the appropriate field/option, change the status to Active, then save your changes.