I have the same problem: the Acrobat Licensing Application window is blank.

I am on a new Mac with macOS 10.15.6 using Acrobat 2020 Pro Student&Teacher. I have just migrated all data and applications including Acrobat from an old Mac. It worked fine on the old Mac. Now with the new Mac, I have problems.

Initially, I tried it with my normal user account (with admin rights). I guess because it's on new hardware Acrobat wants to activate the license again, but I didn't get beyond the empty Acrobat Licensing Application window.

I have tried various things like starting Acrobat with sudo or setting permissions on the folder ~/Library/Application\ Support/Adobe/OOBE  to 0777. Nothing helped. I have uninstalled twice and installed again. Once even moving the complete Adobe folder in Application Support away. No change.

Eventuelly, I logged in another admin account (not root) which never used Acrobat before and there at least I was able to do the activation. Now, at least, I can use Acrobat even with my normal account.

However, I am still not able to sign in. When I click "Sign In" in Acrobat it opens the Acrobat Licensing Application Sign In page, where I click the "Sign In" button. But then I end up again with the empty window. All I can do is quit the application which gives me a warning, if I am sure. So something is still broken...