I have a 2019 13" MBP and a 2017 MBA. I put my MBA into target disk mode and hooked it up to the MBP using an Aukey USB C to USB A cable. The MBA does not appear on my MBP. Do I need some special cable to make this work?
You need a thunderbolt cable for Target Disk Mode, so Apple's Thunderbolt 3 to Thunderbolt 2 adapter and a Thunderbolt 2 male-male cable, to hook up the Thunderbolt 3 port on your 2019 MBP to the Thunderbolt 2 port on your 2017 MBA