Can't see XCTU range test page, it's all gray

Hi, I have installed the XCTU 6.2.0 in Windows 10. I tried to do a range test with Xbee Pro 900-HP using XCTU. However, when I click the ‘range test’, the page popped up is all gray with nothing on it. I can not see anythings on it. I have tried reinstall it for several times and also tried to install it on a Windows 7 computer, but this problem still exists. Is there any way to solve this problem? or does anyone know the reason?

Here is a pic of what I saw:
Here is a pic of what I saw

Re-size both your Desktop resolution to 1024 x 768 or greater and the re-size the window for the range test.