Audio I/O

I/O puzzle!

Have a MacBook Pro ’17 running OS 10.14.4.

Cannot figure out the -Line Input. It seems locked in to

the built in mike and no other input will show.

I have the right cable, since the input is fine on my old

MacBook which has 2 ports for audio, separate in and lout.

It works fine with Garage Band and Audition. Also, when I

attach a Shure mike via USB to the Mac ’17 it recognizes that.

Is there any way to get Line audio into the Mac? Garage Band

Instructions say to select the input with system preferences, 

but it will not show any options besides the built in mike.