You say you appealed on behalf of the Keeper... in what capacity?
The operator has now missed the PoFA window for keeper liability. For a windscreen NtD, PoFA Sch 4 para 8 requires a postal NtK to be
delivered to the keeper not earlier than day 29 and not later than day 56 after the event.
• Parking event: 11 Aug 2025 (Day 0)
• Earliest lawful NtK delivery: 8 Sep 2025 (Day 28 after; delivery Day 29)
• Latest lawful NtK delivery: 6 Oct 2025 (Day 56)
• No NtK was ever delivered. Today is 14 Oct 2025 (Day 64), so the operator has forfeited the right to transfer liability to the keeper under PoFA.
An appeal/rejection (even if addressed to the RK) does not count as, or extend time for, an NtK. Because “delivered” is the test, the last practical posting date would have been Thu 2 Oct 2025 (allowing two working days’ deemed service to land by Mon 6 Oct).
Conclusion: they can pursue the driver only; keeper liability under PoFA is no longer available.
Use that as the core of your IAS appeal, for what it's worth. Irrespective of the alleged contractual breach is, they cannot hold the Keeper liable for the charge if the driver is no identified.
As the IAS is a kangaroo court and their adjudicators are anonymous liars who pretend that they are qualified solicitors (they aren't), they are very likely to reject the appeal on the legally embarrassing grounds that they think they can infer that the Keeper must be the driver.
If the IAS rejects the appeal, so what? Their decision is not binding on the Keeper and they can try and issue a claim in the county court where they wouldn't stand a chance of winning against the Keeper as log as the driver is not identified.