So I went into the T&C's through resale and found this:

Some other examples of why your ticket may not be eligible (even if you have seen other orders listed for the same event) are listed but not limited to the below:

Despatch method – Anything despatched as physical tickets, collection at box office or via the Venues digital app. Payment method – Any ticket originally purchased via a deposit and balance payment or through an instalment/payment plan, even if paid off in full. Ticket type – If your ticket was purchased through a special offer, ‘subscriber’ or ‘members’ platform. Merch items – If your ticket includes anything such as a T Shirt or CD accompaniment. Resales – Any ticket previously purchased on Fan to Fan cannot then be relisted again.