The PCN wording is compliant IMO.
But make reps before 19th April and they'll more likely than not re-offer the discount. IMO, all you've got at this point is a request for them to exercise discretion based upon your first post e.g. not familiar with the area, saw many other cars parked similarly when you parked and was misled by their actions when you should have paid more attention to the road markings. Terribly sorry, hasn't happened before/won't happen again etc...
See if others have views, but don't miss the deadline.