Our advice is NOT TO PAY the Charge Certificate, but wait for the Order for Recovery to be served. This means the CC debt has been registered at the Traffic Enforcement Centre (TEC). The OfR will be the CC charge, plus the TEC fee of £9. This advice is because there is a straightforward process to revert the matter to the original PCN, at which point you can pay it, or submit representations.
In detail, then.....
At the end of the payment period on the CC, phone TEC about 7 days later, then every week or so, to find out if the debt has been registered. Once it has, you can submit a Statutory Declaration to TEC that you did not receive the PCN. The matter will then be reverted to the PCN stage. Of course the paper OfR document may arrive in the post, but with you having missed getting the PCN, take no chances, because you must submit the Statutory Declaration in good time.
You will need to submit a Form PE3 and can download it from this website: -
https://www.gov.uk/government/collections/traffic-enforcement-centre-formsFree to submit, but there will be a small fee for witnessing it if you go to a solicitors. Free at your local county court.