Hi
I have downloaded the latest premium 1.2.96 and installed it.
in Appearance-Generate Press the list of plugins are all active but there is no box on the right to put in the key!
Also getting errors on the Customizer Warning: Creating default object from empty value in /wp-content/themes/generatepress/inc/customizer.php on line 27
You enter your key in: Appearance >> GeneratePress
With the error, I found another thread discussing this, the bottom line was that GeneratePress was not updated to the latest version?
Make sure GeneratePress is on 1.3.46
HTH, Dave