Why would you expect it to be up?
They already put stickied threads in PTR Feedback and PTR Bug Report which said…
10/22 Update
The team is still investigating a few standing issues for the PTR - We’re sharing that the fix won’t be available today. Our goal for this fix is to minimize playthrough disruptions for the remaining time left for the PTR so that players can focus on testing and exploring the content. Ill keep you all posted. Thanks so much for your patience.
The PTR server is in the Pacific time zone, where it’s currently 03:08, i.e. it’s at least six hours before they’ll even be in the office today so don’t expect the PTR to be back up for much longer than that.