Okay! So with that ‘easy theme and plugins upgrade’ I tried uploading the Generatepress .zip folder as a plugin as you mentioned. It worked!
Now WordPress is prompting me that it needs to be updated, so I clicked it and it just directs me to the theme page in my dashboard. It never updates it, per say. With that said I went to Appearance -> Generatepress and can now see a box to the right that says ‘Updates’ and can enter a key. Around this time is when I deactivated the ‘easy theme and plugins upgrade’ plugin.
I entered my key from my account, it refreshed and then ‘License Activated’ shows up on top. Right underneath is ‘GeneratePress has an update available. Update now.’ Clicked update and it took me again to the Theme page on my dashboard. I didn’t notice it before, but a Generatepress theme box is now actually there along with my other (old) themes! YAY!