I am using version build 17A362a on a 2013 27" iMac. I am trying to use my Late 2013 27" imac with a Thunderbolt ports as a second display to my 2017 iMac. I have connected the two iMac's as follows.
2017 tThunderbolt port to Apple Thunderbolt 3 to Thunderbolt 2 adapter. From the adapter i have a Apple Thunderbolt to Thunderbolt cable ending at the Thunderbolt port on the 2013 iMac.
I then used the envokation keys Command & F2 to start Target Display Mode. Result nothing connected.
I then used Fn plus Command plus F2 still no joy.
Is Target Display not availble or am I doing something very wrong.
?