What does the 'Internal Error' drop-off reason mean in Customer Journeys?

Journey drop-offs are now reported with a specific reason, so you should rarely see a bare "Internal Error". Double-click the point of a launched Journey and expand the Drop-off block: each cause is listed with its own count. Reasons are grouped into Internal errors (journey logic/data could not be evaluated for that user) and Sending errors (the message itself could not be delivered).

The documented internal drop-off reasons are:

• User not found — the user was never registered, or was deleted, before reaching the step.
• User mismatch — the device's current UserID no longer matches the UserID that entered the Journey (typical after a logout/login or a UserID reassignment mid-journey).
• Tag not found — a Tag used in Time delay was never set for the user, or a Tag used in Update user profile was deleted after activation.
• Device not found, Filter not found, Rich media not found — an entity referenced by the element no longer exists or does not match the traveller.
• Can't get time — a Time delay could not be computed, e.g. a delay anchored to an event timestamp that is already in the past.
• Request error — an internal request failed for that traveller.
• Emails reached limits, Account suspended — account-level limits or status blocked the step.

Messages suppressed by Frequency capping are not a drop-off reason: they are reported by the capping metrics (number of suppressed messages and number of unique users with at least one suppressed message).

If drop-offs persist, review the configuration of the specific element and the data of the users entering it; if you still cannot explain them, contact support with the journey name and the element in question.