The first step in any apparently missing file is to verify whether the problem is with the file itself. Is this a missing file or a bad reference? If you're missing a key PHP file it'll be pretty obvious right away as your site will be down.
Use FTP to Restore Missing Files
If the file is actually missing, rather than a problem with file permissions where WordPress can't read the file, then the easiest fix is to recopy the missing file or files via FTP.
Make Sure WordPress Can Read the File
If the files are present, then check for a file permissions error to make sure WordPress can read the file.
Missing Site Resources
- Missing files
- File read error
- Reference to the wrong resource
With front-end site resources, like scripts, stylesheets, and images, there are three possibilities. A missing file, a file read error, or a reference to the wrong resource.
The wrong resource usually means that a URL is wrong. This could be because it's referencing your old domain, it's referencing an insecure location on your now secured protocol, or a local host address that isn't available online.
Looks like a Missing File
More often than not, what appears as a missing file is actually a symptom of some other problem.
Artifacts of MySQL Import?
- Did you replace URL references in posts?
- What about older content?
- Did you get the image URL updated?
If you imported your MySQL database manually, for example, you may not have replaced URL references within posts, resulting in references that are out-of-date, even if you used a tool to export data. Some problem URLs may remain 'cause they used some other URL leftover from a prior domain. Identifying in what way a file appears to be missing is key to solving this problem.