This, I used an old board and it didn’t work until I replaced the (button) battery . After that, you can troubleshoot the board adding components one by one and listening to the beeps. There’s a code. Left the GPU as last element and use the integrated one always until all is working. If a external GPU doesn’t work, it could be not enough power. If memory fails, beeps again, try to find a working one and go from there…