offer_ended
Status 409. The campaign has ended, so it can only be removed.
What it means
The campaign's last day has passed. Changing it now would make the orders it paid look wrong, so it can be removed but not changed. Nothing was changed.
What to do
Remove it with POST /stores/{store_key}/programme/offers/{offer_id}/remove, or add a new campaign with POST /stores/{store_key}/programme/offers.
Safe to send again?
No. The same request will get the same answer.
Where you can meet it
POST /stores/{store_key}/programme/offers: Add an offer: a campaign, a product offer or a channel offerPOST /stores/{store_key}/programme/offers/{offer_id}: Change an offerPOST /stores/{store_key}/programme/offers/{offer_id}/remove: Remove an offer
Every code, and the shape of an error answer: Errors.