I give some suggestion for this case.
If the issue occurs, check as follows.
1. Login to the web of the terminal .
Then enter the username/password which is admin/admin by default. go to the device control--video control. When the TV is black, choose video out1. Check whether you can see something here（because the video out 1 connect the tv directly, so it will show whether terminal has output here）
2. If the tv is black. Here it`s black also. Please contact TAC directly and diagnose. If here shows picture. but the tv shows nothing.
The connection is like this.
So if the web shows picture. But the tv shows nothing. It`s caused by the connection cable or tv.
A. Cable issue.
We can find another DVI---HDMI which you are sure works fine. Then connect it with TV. Or we can choose another port of TV（TV has 2 video port）
If works fine, it is cable issue. Or . maybe it`s TV issue.
B. Tv issue.
We can find a laptop connecting the tv directly. And check the result. Whether the same issue as former one. If it is . it`s the TV issue.
After these days diagnose. I found one strange thing. After the tv is black. The red power light in the left bottom lights.
It means it`s sleep mode. Usually after we press the power button. The red light will disappear. Then tv will works. But the local situation is that after you press the power button, it still exits. So please pay attention here. Find the remote and press the power button in the remote .check whether it can work also。
C. Another way is that find a HDMI project or display.
Connect the HDMI to the new display instead. Check whether there is a output coming from the terminal. If there is , tv issue. If there is not. Contact TAC directly.
Then feedback the details.