For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
Do you get all correct voltages?
Start trying new BIOS, clean ME.
Reball SMC, if no result.
Could be RAM/CPU issue and maybe need reflow/reball/change RAM chips.
But start with basic things...