You parked, knew* you were in a parking place because, according to you, you consulted the traffic sign and paid for parking rights via RingGo. But for some reason you didn't mention this in your reps. In their eyes I suspect that not paying marks you as being a chancer whereas payment implies you made a genuine mistake, it certainly is more in your favour than not IMO.
* Or did you not pay and could argue (I doubt successfully) that you didn't know you were in a parking place of any type, let alone disabled, because there weren't any discernible road markings?
IMO, your current line(!) must fail because your own photo shows the parking place markings, the internal transverse line marking the change in restriction and, as observed by others, clear traffic signs where this occurs.