Late 2012 iMac used as target display - Need Help

Have a 2020 iMac 27" and would like to use my 2012 as a secondary target display.

Using Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter

Using Apple Thunderbolt cable (2.0 m)

I did the migration to the new iMac and it used the Thunderbolt cable just fine for data transport.

Catalina 10.15.6 on both machines

What I've tried:

Using every combination of each available port combinations.

Pressing cmd F2 on the 2012 both logged in and logged out.

Using onscreen keyboard to press cmd F2 to make sure it wasn't the keyboard.

Please share what worked for you.