I had the same problem after entering CGC grades for the first time in over a decade. My Grading Sets window had no checkboxes. Mark's hypothesis that the problem may be due to display resolution turned out to be correct (in my case at least).
My Windows 10 Display settings were:
size of text, apps, and other items: 200%
Display resolution: 3200 x 1800
Display orientation: Landscape
The solution that worked for me:
1) If ComicBase is open, Exit ComicBase.
2) Windows Start: Settings -> System -> Display -> Change size of text, apps, and other items: "150% (Recommended)"
3) Open ComicBase
4) ComicBase: Setup -> Grading... -> Grading Sets...
-- window should now include checkboxes!
After exiting ComicBase, I reset "size of text, apps, and other items" to my desired value, until such time that I ever need to add or update comics with a professional grade.
Apologies for not posting this earlier; I was unable to sign on to the forum until now. Thanks to Pete for personally resolving the problem!
