Please check the following reasons:
1, Check whether the record configurations are normal;
2, Select a channel to play back in the Playback interface or enter the Export interface and search the existence of the video in this channel. (this method refers to the local playback)
3, Confirm whether the user account has permission of playback.
4, It’s suggested that customers check the hard drive to make sure if there are bad sectors.
5, Check whether there is exception information for this time period on the log.