Stop sign on Sierra

Hi everyone, I am facing a problem when booting Sierra 10.12.6. It shows stop sign. Recently I upgraded my board, RAM and processor.

I dint find config.plist for my board hence used z370 board config file. It booted but eventually it shows stop sign and if I reboot then it gets booted. So, every time need to boot it twice to get started.

i5 9600K processor Gigabyte z390 Aorus Elite motherboard G skill 8 x 2 gb DDR4 3200 MHZ

Thank you!