Target drive will not show up using target disk mode over thunderbolt
I have a 2011 MacBook Pro and 2013 MacBook Pro connected with a Thunderbolt cable. The 2011 has a Thunderbolt 1 port and the 2013 has a Thunderbolt 2 port. I'm trying to connect them using target disk mode but regardless if I put one machine or the other into target disk mode I cannot see or mount the other disk. I've tried booting both machines into target disk mode and I've looked into System Information to verify that they see each other and they do. In the finder I've made sure that network volumes and drives are checked. I've also checked disk utility and the external drives don't show up. Any ideas? The only thing that I see on Apple's site about using target disk mode mentions Thunderbolt 2, Thunderbolt 3, firewire, and USB C. They make no mention of Thunderbolt 1. Is Thunderbolt 1 now unsupported?