If it appears to be stuck in standby, the first thing to do as with most B&O products, is to disconnect the TV from the mains for 5 minutes. Then reconnect, leave for a couple of minutes then try to switch on again.
If this doesn't work you will need to confirm that the remote is transmitting - this can be done by aiming the remote at your camera phone and pressing a button on the remote - you should be able to see the transmitted IR command on your camera it the remote is working.
If it is then the TV is faulty - on a BV3, that will probably mean chassis and or EEPROM replacement. I would always recommend replacing the chassis and EEPROM for a stuck in standby fault...