external HHD not showing up and disk utility / first aid, but the verify disk and repair are graied
Hello
my external HHD is not showing up anymore on my macbook, I tried with disk utility / first aid, but the verify disk and repair are graied, so I am not sure how to carry on the troubleshooting, could anyone help me?
thank you!
MacBook Air, OS X Mountain Lion (10.8.4)