Mac Pro 15 3 beeps no boot

[jimid454]

2011 15 inch MacBook Pro Three beeps when I try to start Doesn’t even chime nothing I’ve switched out the ram I’m pretty good with computers but I’m dumbfounded??????

 

[kenrivers]

Have you tried resetting System Management Controller?

How to reset SMC on Mac Notebooks

Have you tried resetting PRAM?

How to reset PRAM

"Here’s how to reset your PRAM:

Shut down your machine. Yes, all the way down, not sleep or logging out.
Press the power button and then press command-option-p-r.
You have to make sure you get those keys pressed before the gray screen comes up or it won’t work.
Hold those keys down until your Mac reboots again and you here the startup chime.
Let go of the keys and let your Mac reboot normally."