Unable to run free version of eM Client

Have registered for free version of eM Client. On opening eM Client , the dialog window where you choose between free and pro versions of the program is displayed and I am unable to close this, even though I have put in the activation key. When I now log in, the window is blank. I am running Windows 10. Is there a solution to this please

When you open eM Client, go to Menu > Help > License. Click on the Activate button and enter your license key.