Yes the configuration worked before I upgraded to Mojave. My setup is:
iMac (27-inch, Late 2013, Mojave 10.14.4) and a MacBook Pro (15-inch, Late 2018, Mojave 10.14.4)
Using the Apple Thunderbolt Cable (2.0 m)and the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter to connect both machines.
No this is no the charging cable.
The ports on the iMac are Thunderbolt ports (I have 2 ports) and the ports on the Mac Book are Thunderbolt 3 (USB-C)
I got it to work once upon restarting the iMac but since then it displays a blank screen. I have viewed the link you sent and tried all options which didn't solve my issue. Thanks for the help.