Somebody outside can't register

Where Allow external user self-registration is off, the register button is removed rather than disabled — the page will not show a form that could only fail.

The catch is what it says instead: No registration needed. That is the same message an event shows when it genuinely needs no sign-up, because to a visitor the two look the same. So this message does not confirm that registration was turned off deliberately.

If you meant the event to be invite-only, nothing is wrong and the page is behaving as designed — invite your guests by name and expect the page to keep saying it. If you meant people to sign up, that switch is the fix, and it is on the event in the app rather than in the console.

External participants have a registration window of their own, separate from the one colleagues get. Before it opens the page says Registration not open yet; after it closes, Registration closed.

Check the external window rather than the internal one — an event that colleagues can still join while guests cannot is this, not a fault.

Fully booked means registrations have reached the event’s capacity. Two different ceilings can produce it: the capacity the organiser set, and the attendees-per-event limit on your licence, which applies even when the organiser set a higher number.

Cancelling somebody’s place is what frees a seat — no other status does.

Here the button exists and pressing it fails. Almost always something required was left empty: an external registration form can require company name, phone, job title, department, dietary requirements, accessibility needs and emergency contact, and can require the terms to be accepted before it will submit.

Ask what the page told them. A required field names itself; anything else is worth reporting with the exact wording.