Are you using the Windows version?
The activation screen is a popup that is very quirky in regards to one's screen resolution or scaling in your computer's display settings. For some people it can be missing or blank.
In Windows 10 to get to the scaling or resolution settings click the Windows start button in lower left corner, then choose Settings (gear icon), then System, then Display.
First try the scaling setting. In your Windows Settings do you have scaling set to a higher value than the normal 100%? If so, change it back to 100%. Once the license code is entered and activated, you can later change your scaling setting back like it was.
If lowering the scaling to 100% didn't help, then it may be screen resolution. Try a lower screen resolution such as 800x600. Once you get the license activated, you can revert your resolution setting back like it was.
NOTE: If you happen to encounter a blank popup screen later on in some section of the program, you may have to temporarily perform this maneuver again.
