Mandatory SMC reset at each start after logic board change

Assuming the old Logic Board had no problems, then it most likely indicates that this Logic Board has a hardware issue. Make sure that you have reinstalled the BMU screw and fully seated the flex cable for the Battery. Make sure the latch on the battery cable connection on the Logic Board is down and the connector is not damaged. Also, make sure the other end of the battery flex cable is also fully seated on the battery board and it's latch is closed and the connector is undamaged. Make sure the battery flex cable is also undamaged. This cable & these connectors are very easily damaged.

When attempting to power on the Mac, try connecting the charger. If the charger is already connected, disconnect it for a moment, then reconnect the charger to see if it allows the laptop to power on. Don't perform an SMC Reset. If this does not work, then try connecting the charger to another USB-C port especially on the other side of the laptop. Also make sure to connect the charger directly to the laptop without any adapters.

Make sure to disconnect all external devices except for the charger which is directly connected to the laptop. Make sure you are using the 87W charger and proper charging cable.

These USB-C Macs are very quirky.

The SMC Reset is resetting the power management chip which implies the Logic Board is bad or something is causing this chip to get into a state where it doesn't work properly.

I know from personal experience supporting our organization's laptops, that this model has a lot of quirky behavior with the Logic Board and power issues even on a laptop with no reported issues by the user. It doesn't take much to have power on issues with this laptop. Even the tiniest thing can affect the laptop in ways you may not expect. Troubleshooting these Apple USB-C laptops is not quite the same as troubleshooting older Macs or computers in general.

I've pointed you to things which may contribute to your problem. If those cables & connectors are fine, then it most likely points to a bad Logic Board. The only other thing I neglected to mention is that the contactsw on the USB-C ports should always be examined when working on these laptops since many times they are corroded or even damaged, at the very least they end up with oxidized contacts. An issue with the USB-C port can easily cause issues with the laptop even when nothing is connected to those ports.

If everything else looks Ok, then the Logic Board is most likely the problem here. You have no idea of the history of this replacement Logic Board which is a used part pulled from another laptop. Even purchasing a refurbished part from a respected vendor, there is always a chance of receiving a defective part. Luckily this Logic Board did not produce the same/similiar symptom as the original one or you would be in more of a quandry.

In general, you should not be using the power button to turn off your Mac. the power button does an uncontrolled power-off, as in an emergency.

You should choose "shutdown" off the  menu.