Yes, you can file a new PERM LC with the same employer if it has expired. The DOL does not receive the applicants - the employer receives them. However, if your employer denies a US worker for the position for an unjust reason, that person can contact the DOL and the employer can be in big, big trouble, including suspension from the PERM program, supervised recruitment, etc.
Please also keep in mind that by LAW the EMPLOYEE for which the PERM is being filed is not permitted to be involved in the recruitment process.