Blyss Dehumidifier screen/unit turns off after a few seconds

Hi, I have had this Blyss Dehumidifier (WDH-316DB) for a couple of years. I have not used for 6 months. I plugged in recently, the screen comes on and the unit appears to be starting up then after a few seconds the screen fades out and the unit seams to slowly turn off. It is not the float sensor. After this time if I take the bucket out the full switch still seems to work (it bleeps when I remove it and stops when I return it). Turning the switch off at the mains and on again does not reset it. I have to take it out of the plug then put back in again. Same thing happens again and again – on for a few secs, then screen fade out. Any ideas please?