I don't use a local Python installed, only the embedded with the game.
So the best way is to extract where the exe is, like with the old UnRen.
Launch UnRen-forall.bat, hit enter for the directory (you are already in) and let him select the proper UnRen-[lagacy|current] to be launched by hitting enter.
If it disappears, take a screenshot and send here or if you have a UnRen-forall.log attach it here.
But the best way is to extract in a dedicated directory like C:\Tools\UnRen.
Launch UnRen-forall.bat with admin right and add to the context menu.
After that, you don't need to extract UnRen script in each game directory, you just have to right-click on the game directory (where the exe are) and select launch UnRen-forall.bat, more simple.