Worry not, you haven't received the NtO, so don't pay the CC, (the only option on it), but wait for the Order for Recovery, issued after the council register the PCN with the Traffic Enforcement Centre, then submit a Statutory Declaration that you never received the NtO. The matter will then be reverted to NtO stage at which point you can submit representations, (or pay of course !)'
However, missing the Nto indicates a possible mail problem, so you now need to be proactive, and at the end of the allowed payment period on the CC, phone TEC every 7-8 days to enquire whether the PCN has been registered. Once it has, you don't need the OfR, you can submit the form straightaway, having downloaded it from the TEC website. I think the form you need is TE9, (Witness Statement). Others will confirm or correct me. Reember when filling in the form, the "Applicant" is the council. You are the "Respondent"