If a journey email doesn't send when expected, it's often related to the way the journey was set up, or subscriber data. Below are the most common reasons why a journey email may not have sent when you expected: 

General issues

• Your account has billing issues, usually related to a credit card expiring. In this case, journeys are turned off. After the billing issue has been resolved, make sure to turn the journey back on.
• The journey was not turned on at the time the trigger occurred.
• The subscriber followed a condition step's "No" path, and it had no content. This is often related to conditions based on campaign or journey activity, that don't have a delay step before. As a result, the condition is processed immediately, and subscribers are sent down the "No" path as they weren't given time to engage.
• Email steps were added to the journey after the subscriber had already finished it. A subscriber will only receive those emails if they are part of a date-based journey, and their custom field date means they still fit into the journey's timespan.
• The specific time of day that journey emails are sent is different depending on your time zone and which journey type you choose.

Delay steps

• The subscriber was at a delay step in the journey, and the delay was deleted. This causes subscribers to be removed from the journey. To avoid this, set the delay step to zero instead of deleting it.
• The subscriber was at a delay step that was shortened. Subscribers already at a delay step when it is edited will use the original delay time.
• A delay of a month was inserted, with the expectation this would mean the same day of the month (for example, January 8, February 8, March 8), instead of 30 days.
• Subscribers entering the delay step after it’s been changed will use the new time.

Date-based journeys

• A date-based journey was started, and subscribers had the same date as the journey was started in their custom field. Because journey emails are sent at midnight (the beginning of the day), the trigger time had already passed, and those subscribers did not trigger the journey.
• A subscriber was previously not in a date-based journey, and their custom field date was set in the past to place them part way through. Because the journey contained conditions, they were not allowed to enter.
• A subscriber's custom field date was changed while they were part way through a date-based journey, but their position in the journey did not change because the journey contained conditions.

Subscriber joins a list journeys

• Subscribers were imported from a file, or manually added in the UI, but the person who added them did not check the option to trigger the connected journey. To prevent unintentional and confusing sends this type of journey is not triggered without selecting this option.
• The subscribers were added by bulk via the API (a method used by some third party integrations) but the QueueSubscriptionBasedAutoResponders property was not set to true.
• The subscriber was already on the list being sent to.

Segment-based journeys

• The subscriber was already a member of the segment that triggered the journey.
• For journey emails with a segment-based trigger, we check for segment updates every 10 minutes. Emails are sent when a change is detected. Therefore there may be a delay of up to 10 minutes before the email is sent to a subscriber.
• For new journey emails with a segment-based trigger, there is a short delay before we start monitoring subscribers entering or exiting the segment. This means that a subscriber that enters/exits a segment in the first 10 minutes might not receive the email. Please wait 10 minutes before testing your journey.