Hi,
this is a bug in Corona when the Windows font DPI is changed. There are "cancel" and "next" buttons clipped under the bottom of the window.
You can either
1) blindly use tab key + enter to press the button (there are 2 invisible buttons, so 2 tab keys + enter should work),
2) temporarily change your font DPI to activate Corona (you would only need to do this once), or
3) you could use any of the methods intended for render farms:
https://coronarenderer.freshdesk.com/solution/articles/5000564325-activating-license - for example running licensing server once on the same computer when starting 3ds max.
We are working on the fix, it should be in the next minor release.