Belnea monitor - how to wake it up from sleep/power save?

My Belnea 20inch flat screen monitor (sorry I don't know the model number) works great but if I leave the room for a while then come back, the screen disappears and the blue power on/off light flashes - nothing I press will stop the flashing and bring the monitor back on other than switching it off at the mains for at least 30 seconds. I assume it is some sort of sleep mode but can anyone help me get it to wake up please !!

Thanks