Visit Volcano Aso

I often check on your homepage access to the volcano Aso. Since April 2018 the visit should be possible again.
Is it perhaps possible to visit the Aso in November or is the entrance generally closed?

I had a post on this a few weeks ago. It might be helpful....

https://www.japan-guide.com/forum/quereadisplay.html?0+164764

The link above is more for asking about icy road conditions. Most likely you are asking about the volcanic gas emissions. Currently, some days are open and other days are not or have some restrictions.
Before you go there, it would be wise to look at:
http://www.aso.ne.jp/~volcano/info/

You can get a preview of the area at:
https://youtu.be/Tyh_nKrv5tY

Nobody can predict volcanic activity.

But Mount Aso has been quite calm now for over a year, and I think it is likely that the crater will also be open in two months from now.

Make sure to check again before you visit. Even if the crater is generally open, it still gets quite frequently closed temporarily due to bad weather or strong gases.

This page mentions the daily status:
http://www.aso.ne.jp/~volcano/info/

And this page explains the general state:
https://www.japan-guide.com/e/e4552.html

The road to the crater and the Kusasenri area is open almost all the days of winter. Snow is rare and doesn't last long when it does snow, a reason that the small ski slope closed (where helicopters now give rides). If the wind is from the north or northeast, which isn't too often, the gases are blown into the walking area around the crater at the top of the ropeway, and the crater gets closed off. It sometimes gets cold up there in November so be prepared with a jacket and hat.

Crater visit open/close is erratic mainly by the wind and the gas density. It may close 30 minutes just after it opens. It also suddenly open while you're in Kusasenri.