Advice - Compressor Not Engaging

If you show 100psi on both sides, then there is SOMETHING in the system. If you didn't charge with any refigerant, then you have introduced air somehow. Evacuated for 6hrs, or system held vacuum for 6hrs ?? Evacuating for 20 - 30 minutes is usually sufficient. System must be at least partially charged before compressor will activate due to low pressure cut off switch, as others have indicated.