1.This will occur if you add the trigger tag in advance of us setting up the trigger tag and associating this tag to the email that is to be sent out.

2. Trigger tags only work once they have been set up to be associated to an email campaign.  Once set up they can be applied to your contact - by adding the trigger tag to their contact record, this will trigger the sending of the associated email which is then sent out instantly.  

3.  If you have already added the trigger tags in advance of it being set up by us it won’t work. You need to remove them and then add them again once the associated email has been set up and it will automatically send out the email.