If your DVR's mouse and buttons do not work...

The video output need to be switched from BNC to VGA.

With your mouse plugged in, unplug the power to the unit for 30 sec, then plug it back in. Wait for the DVR to fully initialize, the cameras to come up, & the grid to appear (1 min).

For 4 or 8 CH DVR's, press and hold "REW" on the front panel until the DVR beeps.
For 16 CH DVR's, press "0" (zero) on your remote; the DVR will beep.

Press Menu once. You should now have functionality.

Go to the Main Menu (where you will see 6 icons).

Go to System -> A/V (or Video) set up. Next to OSD DEVICE or INIT. DEV, select your output (VGA or VOUT [for BNC or RCA]), and press Apply.

Then Exit, back to the cameras.