Hello, Ministry Of Concrete,
Our theme searches by title, description, SKU, posts, and pages, but does not search by tags, brands, or categories. For more information, please refer to the following link: https://www.8theme.com/topic/include-brands-in-search-results/.
If you would like to request that this feature be added, you can post your request on our Taskboard at https://www.8theme.com/taskboard/. If it receives enough votes from other customers, our development team will consider adding it in one of our upcoming updates.
About the critical error after the searching, please provide temporary wp-admin and FTP access, so we can take a closer look.
To provide wp-admin access, you can create a new user account with administrator role via the Dashboard, and provide us with the username and password via the Private Content area.
To create FTP access, please contact your hosting provider for assistance.
Thank you for your cooperation and we look forward to hearing from you soon.
Kind Regards,
8theme team