Update — I installed a new instance on the same server as my dev site just to test. I pasted the license and even though I check the “agree” box, the submit button remained unclickable. That was version 5.5 of WordPress, same as the one in the new server.
So I installed another new instance of WordPress using 5.4.x and it let me register the theme. Since WP 5.5 just came out 2 days ago I wonder if that is an issue that needs to be checked since I had the same problem on the same new version on 2 different servers.
Took my actual dev site and downgraded it to 5.4.x…and voila….the Register button works. Definitely an issue with 5.5.















