They don't, and I did or I wouldn't be asking on this forum.I didnt say there was a "synch" button. Simply tick the checkboxes for the cameras you want to view on the right and click n the timeline. All cameras will start playback in synch.
You really need to make an effort and try some shit on your own
*And use IE or there are buttons and functions you wont otherwise see
Done all that, little buddy. And you're mistaking criticizing with whining, probably typical for you, used to take it like a champuse internet explorer or smart pss
and stop whining so hard. read the manual or find out how things work yourself. these nvrs are easy and everything is self explanatory.