How to register Adobe Acrobat 2020 Trial - purchase not detected

Depressing how awful I'm finding the design of Acrobat 2020. I bought an education version. You have to install a trial and then get the serial number. I received it. Serious problems:

Preface: I created a new Adobe account and registered the serial number which I see as an Acrobat 2020 purchase in my adobe profile. I login with the email address in the app but no purchase detected. No place to enter the serial number in the app.

1. I've spent hours trying to find the area to register the serial number in the app. Not in the menu (typically in help area, preferences, etc.) It's simply not there.

2. I've tried to click the "activate" button when it shows in a blue box. That tells me the purchase wasn't detected.

After going through the entire installation and update which took a very long time, it seems I'm left with uninstalling everything and then reinstalling everything, hoping the serial number will work upon entry, then updating again with th updater. This is extremely subpar. There's a good amount more I find extremely mediocre on the 2020 edition but perhaps this has been a long trend in the standalone sofwtare edition.