keybindings – external keyboard: cannot use f1,f2 etc. keys without pressing fn key

I am using mba with high sierra and an external keyboard JETech 2156. The problem is I do not want to use fn key, for example F8 key has play or pause option. I have to press fn+f8 to pause or play. I simply want to press f8 rather than pressing fn key every time.

In the keyboard settings the box next to use f1, f2 as std function keys is unchecked. It does not matter if this box is checked or unchecked. In modifier keys I’ve selected the JETech 2156.