techy

Hello, I currently am a security consultant for multiple companies. An employer has CCTV cameras on a loop constantly streaming, this video footage gets backed up into multiple .mp4 files. Now im not sure the exact model of the CCTV system. But i think its a samsung. I cannot view these .mp4 files, i have tried multiple players and codec updates with no luck. Can someone please explain to me how to view this footage? or at least explain what i need to do? cheers!