Okay,
I was going to recommend that if you log in to the NVR with a browser you should be able to configure Virtual Host which will allow you to log in each and reset passwords, but obviously that requires you to know the camera password.
Unfortunately, your only option will be to either plug each camera into a separate PoE injector/switch and export the reset file using SADP to then get your original supplier to password reset each camera, or you will have to get hands-on with each camera and do a manual hard reset using the physical reset button on each camera.