We’ve disabled YITH WooCommerce Ajax Search Premium plugin and fixed the SKU search problem (via the child theme). You can clear cache and check.
Please do not use additional search plugins together with our Ajax search, because it generates errors.
I would recommend you to disable some plugins, for example, WPML All Import and Regenerate Thumbnails. Also, you have plugins with similar functionality WP Google Maps and GMAPS for Visual Composer. When you have multiple plugins installed and activated on your site, it can slow it down. So, keep enabled only those plugins that you really need for the correct functioning of your site and disable all the plugin that you don’t use.
If you want to use this option https://prnt.sc/jl3v1o, you need to enable debug mode and fix any problems come from plugins.