Hello,
Thank you very much for choosing our theme and for contacting us.
I see this message when trying to check the settings in Appearance > Themes The site is having technical problems. Check the site administrator’s inbox for instructions.
Please deactivate all the plugins not related to the theme and switch the parent theme if you run the child, check the issue #3, if the problem remains, leave the plugins not activated and provide the site admin access to the private area
As for the Wishlist:
1. Create a page and insert the shortcode [yith_wcwl_wishlist]
2. Navigate to Wishlist plugin and set the page: http://prntscr.com/ls1ewo
As for the plugin, perhaps it is not compatible. Please check it on the Storefront theme.
Best Regards