I opened this question.
Dan marked the question as answered and now I can no longer reply. The text boxes are available to type, but there is no Post/Reply/OK button:

The articles linked by Dan are not related to my issue. The migration assistant is up-to-date as it was just installed by your application's plugin manager today.
Attempting to go to open a ticket at support.atlassian.com, also suggested by Dan, refers me back to this site.
Please provide further assistance with this is
- Josh