Unfortunately this is unrelated to the plugin, the server does not allow access to that file. The file exists, as the error only states that based on a .htaccess rule it can’t allow loading the file, it denies permission.
If the .htaccess was not changed, then it has a malformed mod_rewrite rule, which triggers for this specific path or path model. I strongly recommend reviewing the all of the rules, it is more than likely the source of the issue.
Checking the file access permissions for accessing certain file types on the server configuration can also help, however this seems to be only affecting this specific structure, so it is much more likely a mod_rewrite rule problem.
This file and it’s location was not changed for over 3 years.