Ender 3 V3 Heatbed not heating properly

My ender 3 v3 recently started to have error “key:2565 Heatbed not heating properly”. I was in the middle of printing and I notice the heatbed temperature was going down so I manually set the temperature to 65C and it did rise back to 65C but after that it goes down again, the print stop and the error popped up. I turned the printer on and off, then set the temperature to 50 to see if the heatbed will heat up, it stayed at room temperature and will not heat up at all. I checked the wiring and nothing was loose. does anyone know how to troubleshoot?

I really need to print my university project by the end of this week. this is really a bad timing for me

Sorry seems your bed is not working fine.

When you rise manually the temp, did the bed get hot or remains at room temp? i am trying to see if the problem is the heater or the thermometer

The heatbed remains at room temp, the temperature doesn’t increase

So is the heater part of the bed, bad luck you must change the bed.