This is not just a Linux issue but a general issue most software or hardware players cannot play the resulting exported/backed up format of .h264 from DVR security camera footage for some silly reason.
There is a simple solution in Linux using ffmpeg fortunately.
Convert the .h264 file into mp4
ffmpeg -i yourfile.h264 -codec copy video.mp4
play dvr .h264 file
ffplay -f h264