Ok @kennywyland you're not the only one seeing this. Same here. Try to hit the + button to add a new version and I get an empty Agreement Update dialog.

Thought maybe trying it Safari would make it work since I've seen that in the past. But no, even Safari is broken...

Related: https://developer.apple.com/forums/thread/661193?answerId=634918022&page=1#634947022

Looks like they fixed it. I'm able to press + to create a new version and get the dialog to enter a version number. :)