Alex, a couple of quick thoughts.
1) When you're working on the Columns and Rows shelves, Dimensions always come before Measures. That's just the way it is: there's nothing you can do to change it.
2) Right-click on the x-axis (anywhere, but on the axis, not on the bars) and select "Show missing values". That will put the months with no values back into the viz.
Thanks for the welcome. I will have to rebuild the report with some dummy data and I will try to put it up later.
The groups "blue pill" and date "green pill" are both listed as "Dimensions" in my data column.
Show missing values seems to have done the trick. Actually I guess the real problem was that I had null values filter out. Thanks for the help.
Glad that worked.
And sorry - posting with insufficient coffee, obviously. DISCRETE pills come before CONTINUOUS pills on shelves should have been what I wrote.