That's hard to answer with the information provided. In general
- Check that the dollar sign expansion returns a date value with the same format as the field you are modifying ([Calendar Date]).
- If you remove the expression label in a straight table chart, you can hover over the label and see the expanded expression, to check that all dollar sign expansions work as intended
- Check that there are values for your field modifier search to return (i.e. Calendar Dates before the expanded date).
- Also check that potential user selections or other field modifier don't render the set incompatible (e.g. check the field modifications for Calendar Year Month ID is compatible to your Calendar Date selection and all possible user selections in calendar fields.
As you see, multiple possible causes why the expression might not work. It's often much easier to help if you could post a small sample QVW.