Registering online for self-assessment and National Insurance

The HMRC web page for registering online for self-assessment and NIC (https://online.hmrc.gov.uk/shortforms/form/CWF1ST?dept-name=CWF1&sub-dept ) has been down for several days, with no mention of it on their availability/down-time page. The help line is playing a recorded message saying they are very busy and to call back. How can I find out if it is ever going to come back up again?