Why Is My Mac Making Three Beeping Sounds During Startup?
If your Mac is making the dreaded three beeps of death during startup then you definitely have a RAM issue of some kind. Possibilities include dislodged RAM, bad RAM, or incompatible RAM.
The first step is to remove the RAM and reinstall it to see if that fixes the issue. If that doesn't work and you have previously upgraded the RAM, trying removing the new RAM and putting the original RAM back in your Mac. If that fails or you are unable to take that step, it's best to make an appointment at the Apple Store Genius Bar or your local Mac specialist.