At time of writing the ATO website is down.
The site states there is an "Unknown error".
There is a chance this error is related to scheduled maintenance, but the maintenance was supposed to be completed yesterday.
Reminder: Our systems are unavailable 10pm Thu 13 Apr to 6am Tue 18 Apr (AEST). Our offices & contact centres will be closed for Easter. pic.twitter.com/RKhqmywN77
— ato.gov.au (@ato_gov_au) April 11, 2017
We've contacted the ATO and will update when and if we hear back.
The ATO recently tweeted the following:
@StreamlineAccts We're investigating current issues with our website as a priority. We apologise for the inconvenience. ^AE
— ato.gov.au (@ato_gov_au) April 18, 2017
Obviously people are aware of the issue and working through it.