What is: Polling expired, please try later?

Sometimes a submission sent from AW-APPS Payroll to the HMRC RTI system does not receive a response after a set number of attempts. This can happen when HMRC systems develop technical problems. In this situation, AW-APPS reports that polling has expired and does not commit the payroll. It has to be run again later from the Run tab. HMRC is aware of these issues as soon as they arise and fixes them as soon as it can, so it is usually just a case of trying to run the payroll again after an hour or so.