I hope you are well today and thank you for your question.
I suppose you have enabled the theme option as shown in the attached screenshot which works fine for me using latest version of Jevelin theme.
If it doesn’t work for you using below latest version of Jevelin theme then this can be due to plugin conflict on your site so please try temporary deactivating all plugins except Unyson plugin and see whether everything works fine and then enable the plugins one by one to see which plugin is conflicting if any.
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Also could you please share me your site URL where it’s happening so that i can troubleshoot it?
Thank you for the swift reply. It turned out to be a conflict with the Mega Menu plugin. Once disabled, it works perfectly fine. Can you, however, recommend a plugin that allows me to modify the menu design in a similar style without disabling the smooth scrolling feature?
Solution for this topic
You can use Unyson Mega Menu by activating Unyson Mega Menu extension and then use it in the Menus as shown in the attached screenshots.
You will find more information about it in the following page.