Ok.
I made a clean environment. New B4J, new JAVA 9, new ABMaterial 4.51 with feedback server, all browsers cleared to zero.
I run DEMO and it does not work (FileManager).
Surprisingly, it works partly on InternetExlorer only !!! But you can not see icons (paste, cut, etc) and folder names. There is no reaction on Chrome or Opera.
Everything works properly on every browser in ABMaterial 4.30 and I see that others have a problem with that.
Well, I had to recompile the client's webapp to version 4.30 until it somehow solves it differently.
I do not know why it works for you?