Output device changed but not getting sound output

I am using macOS Mojave v10.14.5. After I plugged in my headphones (while the MacBook is not plugged into power and opening KMPlayer to listen music on speakers), I was unable to get the sound output my headphone. Still the actual sound came out from MacBook Pro speakers instead of headphones. Any idea on this issue?

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Solution 1:

Are you sure KMPlayer is not overriding the default speaker setup? Have you tried going to Main Controls > Audio > Audio Renderer and setting your device as default?