internal error when I change person password

I am trying to change the password for a person from the interface but I get the following error
when i click the send button.
this is the breadcrumb
Inicio > Administración de Usuario > Administrar Usuarios > Restablecer Contraseña de Usuario
Error message

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at [no address given] to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Hmmm, interesting. Generally an internal error is related the the server configuration in some way (missing extensions, for example, or a syntax error in the .htaccess), but if you’re only seeing this with the Password Reset option then it may be something related to the file itself.

Once place to start may be checking the file permissions of modules/User Admin/user_manage_passwordProcess.php, then perhaps also look in your server's error logs for more detail. Often these are found in <code class="CodeInline">/var/log/apache2/error.log or /var/log/httpd/error.log`.