A message from the application vendor has appeared in our Self Assessment application advising "We are receiving reports that access to HMRC Agent Portal ... has been suspended. The only functionality affected is the ability to log in directly to HMRC's agent Portal ... typically to view your client's liabilities and statements, without having to manually enter Government Gateway credentials via HMRC's own website".
It sounds like something (unplanned?) has changed at HMRC side.
Does anyone know anything more about this?