No leds normally mean R. I. P.
go over the soldering with a magnifier or continuity tester. If BF ain't opening try a different lead
different com port
different baud rate
But if it ain't opening, it ain't opening.
So suck it up dig deep & be more careful next time. Just buy the cheapest F4 you can. In fact buy two so you ain't got to wait so long the next time you fry one.
Have you got any pictures of the crime scene for us to look
at as evidence.
Oh just one more thing sir,
Did you mess with the ports as that's a killer. You can't brick it like the old naze, so other than a short or physical damage that's the only way to be locked out.
How are you supplying 5v to the fcb?
Esc or pdb to 5v rail.