Easy one to win but takes a little bit of effort. ECP are on a roll right now and have been issuing thousands of these "old" PCNs.
As you are way past the POPLA appeal period, before this goes to litigation (it will), there is one more card to play...
As you are able to evidence that you never received a POPLA code because ECP emailed the appeal rejection to the wrong email address, you should complain (not appeal) to ECP that under the BPA Code of Practice, section 23.12 which states:
23.12 Where you reject an appeal against a parking charge notice, you must present the driver, keeper or hire company with the option to:
a) pay the parking charge; or
b) appeal the decision to POPLA
• You must tell the motorist how to make an appeal to POPLA. This includes providing a template ‘notice of appeal’ form or a link to the appropriate website for lodging an appeal and a valid 10-digit verification code. Even if the verification code is automatically printed on an enclosed appeal form, it must still be in a prominent position on the first page of the rejection letter.
• You must give the motorist a reasonable amount of time to pay the charge before restarting the collection process. We recommend that you allow at least 35 days from the date you rejected the challenge.
As you have evidence that they have not complied with that requirement, because you can see from their evidence, that the rejection of the appeal together with the POPLA code was emailed by them to the wrong email address, they should put any enforcement action on hold and resend you the appeal rejection together with the POPLA code and to reset the appeals process clock (giving you 28 days from the (new) appeal rejection date.
These are (some of) the BPA CoP rules they must comply with following receipt of a complaint:
23.24. A complaint must be acknowledged by you within 14 days of its receipt unless exceptional circumstances apply, in which case the complainant must be kept informed by you.
For a small operator there might from time to time be limited administrative capacity to handle communications, e.g. due to staff sickness.
23.25. A full response to a complaint must be provided by you within 28 days of its receipt unless exceptional circumstances apply, in which case the complainant must be kept informed by you.
As the complaint is about the appeals process being incomplete due to ECPs error, you may want to highlight section 23.12a of the BPA CoP:
23.12a If an appeal is being considered by POPLA, the debt recovery process must not be commenced/recommenced until the outcome of the case is known. We would expect operators to have systems in place to ensure that this does not happen.
In this case, the outcome was never sent to you, therefore the debt recovery process should be suspended.
Failure by ECP to comply with your request will lead to a formal complaint to the BPA. If they continue to brush you off with the "deal with the debt collector", then go straight to a BPA complaint with the evidence. Normally the BPA will tell you to go through the operators complaints procedure first and exhaust that. If ECP will not accept your complaint then go straight to the BPA.
Only issue is that the BPA are incestuously intertwined with their member paymasters, the operators.