I upgraded recently to the latest version my license covers, 6.20.1, after a period of not using AB. I find that clicking on the 'Monthly view' or 'Weekly view' button has no effect; the Daily view remains. Hovering over these buttons lights them up, but that's all that I can make happen.
I have always run AB in Parallels on a Mac, but this is the first time AB has not worked perfectly for me.