In config the paths you see are suggestions as to where they might typically be found ... they are not actually discovered paths by moodle code.
An X next to the box means your moodle cannot find it.
From command line see if the path is pointed to an alias.
ls -l /usr/bin/gs/
If you see: lrwxrwxrwx that's a symlink/alias and to the right you will see the real path your system is using for that symlink/alias.
Also use 'which ghostscript' to see from the command line environment where ghostscript is located.
Use the real path.
Also check web service error logs as well as a secure log for hints/clues.
'SoS', Ken