The path may in fact exist, but if it isn't readable by the qubeproxy user, you will still get this error. Qube ships in the default mode "proxy," which means the job is executed by the proxy user. Qube installs a default user called "qubeproxy," which must be able to access this file.
You'll need to adjust your server configuration to include qubeproxy in the group of users that has access to the file.
