I appreciate the update that you gave , @nicola231.
I have some information to share about the message that you received upon submitting your FPS to HMRC.
We currently have an ongoing issue wherein customers are unable to submit FPS and received the error "There was an issue submitting your filing. Wait a moment and try again. If the problem continues, contact us".
I'd like to let you know that our engineers are now investigating the root cause of this issue so they can come up with a permanent resolution.
To be notified of the current status of this matter, I recommend contacting our Customer Care Team. This way, you'll be added to the list of the affected users and send you an email once any updates of this hurdle are made available.
Your patience and understanding in this situation are much appreciated.
For your reference about the FPS submission, here are some link that you can check out on how to do this successfully depending on your payroll subscription:
You'll want to make sure that you've reported real-time information (RTI) to HMRC, including the payments, deductions, and contributions to successfully submit FPS to HMRC. Also, it's recommended that you set ur for RTI before running payroll even if you don't pay an employee for a tax month.
This is to ensure that payroll tax information is submitted to HMRC. Please check this article for more information: Turn On RTI Reporting to HMRC.