Hi stan,
You have not mentioned which software provider you are using.
If it is HMRC's Basic PAYE Tools, you will need to speak with our Online Services helpdesk (0300 200 3600) regarding rolling the software back in order to submit the missed FPS.
Technical support with HMRC online services
If you are using a commercial software package, you will need to call them to discuss how to correct this.
Thank you.