Hi,

Have you update the WP to version 5.8? If yes, let's check again with your plugins. Maybe you're using a plugin doesn't compatible with WordPress version 5.8. We've checked and this theme works fine with WordPress 5.8. And from WordPress 5.8, the widgets will changes the interface.

Please try to deactivate all plugins ( except plugins come from the theme ) and try it again. If it works, let's enable each plugin to check what's plugin caused this issue. 

And if you want to go back to manage widgets like before, you can install plugin:

https://wordpress.org/plugins/classic-widgets/

Best Regards,

PenciDesign