Further trials from my side
I installed menu icons plugin https://wordpress.org/plugins/menu-icons/ and tried using it, again the icons don’t appear however when I change to a different theme the assigned icon appears, please check attached image.
The below is mentioned in the FAQ section for the plugin
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The icons are not showing!
Make sure that your active theme is using the default walker for displaying the nav menu. If it’s using its own custom walker, make sure that the menu item titles are filterable (please consult your theme author about this).
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