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It is almost certain that power is not getting to the monitor. Again you need to check the power cables to the monitor and make sure that they have not come loose. There are two ways of connecting power to a monitor; one is via a 'piggy-back' cable - that is one that plugs into the back of the computer, (the system box). Changes in regulations require that (for all new computers) monitors need a cable to connect directly to a wall outlet.
Note that there are two cables connected to your monitor. One is for power, and the other connected to the back of the system box, supplies the signal (the picture). Make sure that both are disconnected before you try to move the monitor!
If yours is a 'piggy-back' cable, try using a direct connection to a wall socket. If that works, there may be a fault with the cable. Alternatively there could be a problem with the power supply inside the system box (in either case consult with an engineer).
Remember the secret of successful fault finding is to eliminate likely faults one by one!