Where is the power button located at on a 32 inch 400bx commercial display. It has rear power switch and remote power button too. what do I do? Is there a manual?

The power button is the right-most button closest to the right side of the monitor.

Could be as simple as replacing the battery for the remote. Try using the power button on the Tv to switch on. If not OK. Unplug it and let it sit unplugged for an hour or so. Reconnect and try to on. if not OK then have a look at the power supply board.

1. Turn on your TV.
2. Press TV on your remote. ...
3. Enter 9-9-1 and the TV button will flash twice.
4. Press 1 and the TV button will flash twice.
5. Press the Power button, then press CH+ multiple times until the TV turns offs.
6. Once the TV turns off, press Setup to lock in the code.

Has the power button on the TV been used often or not? If so it could be worn out/stuck and the two button leads making unwanted contact.

Consider how the switch will be used before choosing a mounting location. Check for rear clearance before drilling a 9/32-inch hole and mounting the switch.The GRAY wire in the two-pin plug may also be used as a (+) ghost switch input and can be connected to any (+) switch in the vehicle. (See Feature Descriptions section of this guide.)

This is from the installation manual for the Viper 300. To answer your question, it is probably camoflaged. They only needed to tie +12vdc to the input line. What does this mean? Well, my best guess is, they are using one of your switches on your dash to act as the Valet function. Look for where the Gray wire, from the wiring harness of the Viper goes to: that WILL BE your hidden Valet switch. Best of luck!

Viper 300 ESP Installation Manual Plug in Harnesses Super Bright Led Valet...

one or more of the tiny switches on that board with the controls is bad--either replace the board with the controls or just use the remote.

The plastic buttons will seem fine--it is the tiny switches under them that causes this issue.

To turn on the TV:

Turning the Display On and Off
There is a power switch on the bottom of the display and a power button on top. The power switch is used to cut off power completely, whereas the power button turns the screen off but
allows the remote to continue working.
To turn the display on:
1. If the power light on the front of the display is off, turn on the power switch on the bottom of the display.
2. Press the POWER button.

To turn the display off:
1. Press the POWER button.
2. If the display will be unused for an extended period of time, turn off the power switch on the bottom of the display and disconnect the power.

Please make sure you rate my answer 4 thumbs up! Thanks so much for understanding, it would be a huge help to me. I would be forever grateful if you could do this for me. If you still have a question or concern about this problem please just respond / reply to my answer here before rating my answer.

Thanks
Tim

Turning the Display On and Off
There is a power switch on the bottom of the display and a power button on top. The power
switch is used to cut off power completely, whereas the power button turns the screen off but
allows the remote to continue working.
To turn the display on:
1. If the power light on the front of the display is off, turn on the power switch on the bottom
of the display.
2. Press the POWER button.
To turn the display off:
1. Press the POWER button.
2. If the display will be unused for an extended period of time, turn off the power switch on the
bottom of the display and disconnect the power.


Allso go here for full manual:

http://www.retrevo.com/search/v2/jsp/mytrevo/myTrevo.jsp?page=man

Sounds like you need to get a Green Setup remote but if you are using this privately you will not be able to obtain one to program the tv. They are only available to hotels since the tv's are for commercial use.

* With the TV in standby, press the {INFO} {MENU} {MUTE} {POWER} buttons on the remote.
* The TV will turn On with the Service Menu displayed.
go to reset
* Press the {POWER} button to exit the Service Menu.