Help with H815

Hi. I upgrade an LG H815 from 5.1.1 to 6.0 with octopus and screen stays black after set turns on. I used LG Bridge and it recognizes the set as H818. I flashed via LGUP with H818 firmware and still black screeen. But now I can’t flash it back to h815. Any way of solving this issue??
Could I use Medusa pro to erase and flash eMMC again to H815 and getting it to work again?? PLease help.