Windows makes it very easy to launch two copies of Graphical Analysis at the same time. You’ll be able to tell this is happening on Windows 10 by looking at the Windows taskbar icon and looking to see if you have a shadow on the icon, and also when you mouse over the icon it will show you two preview windows.
Don’t do this. The second copy of Graphical Analysis is useless: it can’t collect data and can’t open files and you can’t even manually enter data. If you attempt to open a file with the second copy it will allow you to select the file you’d like to open, but it won’t display anything. Just close the second window and try to open your file in the first window. If you aren’t sure which window is which, close them both, and then relaunch the app so you are sure you are in the one that works.

The same thing will happen if you have Logger Pro running, and then launch Graphical Analysis.

Windows: Graphical Analysis app data table is missing headers or has no cells