If a camera is detecting motion but is not recording, it usually means that camera is not scheduled to record on motion. On the video recorder, navigate to the Main Menu > Setting > Schedule menu and make sure that motion detect (MD) is enabled for the desired period.
If the camera is still not recording, make sure that the proper record channel is selected for the camera. Go to Main Menu > Setting > Detect menu and check each channel in question to enable the desired record channel.
Also verify that the video recorder is set to record on schedule. To do so, go to Main Menu > Advanced > Record and select Schedule for all the channels to be recorded on motion detect schedule.
If the camera is still not recording, check the HDD status by going to Main Menu > Info > HDD Info menu to make sure the HDD status and S.M.A.R.T. Is Normal. If either status is different than normal, or any of the above steps, please contact technical support.