Icons Not Showing in Top Bar of GUI Xfce Desktop Environment

Hi all,

I am wondering how to fix this:
the icons of minimize and maximize at top bar of this GUI is not showing

https://www.linuxquestions.org/quest...1&d=1689682287

where is the the file for configuration to show icons? Is it better to choose oxygen or breeze icons set?

Thanks.
Attached Thumbnails