Very new to update queries.

so I’ve tried creating a Wordpress plugin that searches data in a different MySQL database and it works when I search by license number but when I search for any kind of name I get sent to a “Page not found” page and I can’t figure out how to fix it.

Wordpress INDEX FILE Deleted automatically on cloudways server Even no Malware on the site present.
why this is happening I have even changed the file permissions.Everything updated on the website.
Please help me to resolve this.