Hello-sorry to hear your Mac doesn’t boot. First try zapping pram and resetting the smc- how to do that can be found on the support section of apple’s website, or use google. Then plug in your power cord and go for internet recovery( option+ apple+r keys held down on restart) you’ll probably have to have an Ethernet cable plugged into your Mac or wifi turned on. If that doesn’t work, try straight recovery( Apple+r keys held down on reboot) and see what that does. If it still doesn’t boot at all, maybe time to take it into your local Apple place, or try someone else here
John b