What?! That last reply was an addendum to one that evidently wasn't sent! So here it is again, for the first time...
I discovered this when I was installing Premiere onto a new laptop but then discovered it's happening with the old one too, so it's for Windows 10 and 11, Premiere 15 (20160905.daily.1036636).
But I've been using 15 since it came out and never had this problem (though I haven't changed any keyboard customizations in many years).
I go to Edit/Keyboard Customization, then highlight a command and enter a key or keyboard combination... and nothing happens.
I've tried clearing a command I already have then entering the same command and, again, nothing.
Here's a screenshot of a command highlighted, and to see what happens after I click a key, just look at the same screenshot – nothing happens.

Based on your screen shot, I duplicated the issue. If I select the command in the left column, it is not responsive and the buttons are greyed out. Oddly, if I select the same command in the right column (with my mouse), it works fine.