When I open my notebook application on Windows 10 I get a completely blank window, see the attached .png file. There is no notebook or any hint that notebooks exist. Furthermore, the application always asks me to sign in again *every* time I start it. So somehow it loses my login information.

When I login using Chrome I can see and use my notebooks, so I know they exist and that I am using the right sign-in information. The blank screen in the Windows executable is new behavior. Notebook worked just fine last week.

I tried rebooting and also downloading and installing the latest 64-bit version of Notebook. This made no difference.  I am running Windows 10 2004.

Please help.