Sorry to hear of the problem you are having.
Does the plugin work fine after activating any default WordPress theme like TWenty Seventeen?
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.
If it doesn’t work with default theme also then it is plugin issue so please contact the plugin support on the following page.
We only provide support to Jevelin theme here and provising support to plugin is beyond the scope of support that we provide here. Please see https://themeforest.net/item/jevelin-multipurpose-premium-responsive-wordpress-theme/14728833/support