Why DVR can not power up?

When you connect DVR with power, but DVR can not be powered on/Start/running. Please check below points. 

1. Normally, we may test DVR in office/home with a normal power adapter, in this condition, please connect DVR power wires like below. 

Red+yellow wire tie together, and connect to power +12V.

Black wire connect to power GND. 

2. When we install DVR on vehicle.

Red wire connect to car battery +12V.

yellow wire connect to car ignition wire (Car ACC).

Black wire connect to car battery GND. 

3. I made correct connection with power, why DVR still not power on?

Please check if the front panel be locked.