Question Motherboard replacement of HP 15t-Q300 notebook

Feb 3, 2020
Recently I changed the motherboard (15CBHPGT) of my old laptop (HP envy 15t Q300) after HP-service confirmed the board was damaged. Now after changing the board and connecting only the power cord without the battery, the power LED is turning on but pressing the power button is not turning it on. No power to fan or HDD. I checked by disconnecting each connection, Ram, HDD, display but nothing solved the issue. I have checked the 19.5V to the board and the 3V to the power button. This is happening with the new motherboard. Can you suggest what I can check now?
Where did you get the motherboard from?

check all connections again

was a CPU installed in the new motherboard?

RAM is correctly placed into the board?

Is the power button connected?

Might be dead on arrival

check the BIOS battery, is the plus symbol visible/upside?
remove the BIOS battery, press the power button for about 20seconds, after that install the BIOS battery again

Try it with the battery pack in place