Photoshop installer not opening on Mac OS Catalina 10.15.5

I'm trying to download a trial version of photoshop. 

I just upgraded my Mac OS to Catalina 10.15.5. 

I've downloaded the Photoshop installer onto my Applications folder.

When I click to run it, it opens a window like this one, but then when I double click on the icon, NOTHING happens. Nothing opens, nothing. The only difference is that I see a little "harddrive" icon on my desktop that says Photoshop Installer. 

I've tried so many things and nothing works: 

- ejecting the installer and trying again 

- deleting the .dmg file and redownloading it

- restarting my computer

- deleting all other older versions of photoshop on my computer

.... 

help please!!