Erase Computer for Trade In

Teachyou wrote:

I have tried those steps and the button is still greeted out.

?

You can not erase a drive if you are booted from that same drive.

if you still have issues—

Call Customer Support  (800) MY–APPLE (800–692–7753)

or on line  https://getsupport.apple.com/

or

Outside the USA—Contact Apple for support and service by phone

See a list of Apple phone numbers around the world.

https://support.apple.com/en-us/HT20123

Teachyou wrote:

I am trying to erase my Mac to turn in for a trade. I have followed the above steps but my erase button is grayed out. How can I fix this? Thank you.

Same as here—What to do before you sell, give away, or trade in your Mac