Question A problem with a desktop computer

[DM777]

Hello everyone. A desktop computer suddenly does not turn on. I removed all the hardware from the motherboard, and only connected the power supply. When the power cable is connected to the processor there is a flash of one second and that's it. When I disconnect this power cable, the response is longer. This happens even when all the hardware is connected to the motherboard . What is the problem here.. I would appreciate your help. Thank you all. (Sorry, I don't know how to upload videos here for illustration).
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Motherboard: GIGABYTE B460M.
Processor: INTEL CORE i5 10400.
Graphics card: ASUS PHOENIX GTX 1650 4G.
Memory: KINGSTON 8G DDR4 3200MHZ.
Power supply: ANTEC ATOM 550W.
SSD: Transcend 512GB.

 

[rgd1101]

full system spec? include brand and model of the psu

 

[DM777]

Thanks for your response.
Motherboard: GIGABYTE B460M.
Processor: INTEL CORE i5 10400.
Graphics card: ASUS PHOENIX GTX 1650 4G.
Memory: KINGSTON 8G DDR4 3200MHZ.
Power supply: ANTEC ATOM 550W.
SSD: Transcend 512GB.