Mount Aso: current state of Nakadake?

What is the current situation with Nake_dake . Is it possible to access the crater + also what is The JR train network like ? Is it fully working I am planning to visit the area in September, I accept that it could change by the hour but I am wondering what the current situation is. I will be using public transport. Thanks Graham

The crater cannot currently be approached. The situation is explained here:
https://www.japan-guide.com/e/e4552.html

As for the train network, the line between Kumamoto and Aso is still interrupted between Higo-Ozu and Aso. I believe that they try to get it reopened by spring 2021. You can take buses, instead, while a rental car is most convenient to get around the area. More details are here:
https://www.japan-guide.com/e/e4551.html

You can see the current official status here:
http://www.aso.ne.jp/~volcano/info/

You have to stay 1 km from the crater rim. And honestly, I would not get your hopes up on that changing. Since 2014 it has been like that except for a brief window when it was open again. You can see what it used to be like though here:
https://youtu.be/Tyh_nKrv5tY

If you have a car, there are indeed many very good natural sights in the area - Nabegataki Falls, the Daikanbo Lookout, Kikuchi Gorge, the Yamabuki Springhead, and more. Very worthwhile.
https://goo.gl/RwpnU8