X-Axis Dates Missing Even with Date Table

I'm struggling to understand why I'm missing dates on my x-axis even though I'm using dates from my Date Table. 

In my model, I'm joining DimVendor to Capacity, then Capacity joins to DimDate on a standard date value (yes, DimDate is marked as the date table). 

On my report, I have a slicer, limiting DimVendor to a single vendor. Then a relative date slicer. No other filters on the report.

My line chart visual uses a Year-Month hierarchy for the x-axis, then a measure that simply sums a Capacity column (this measure is located in a measures table). You can see from the images that I'm missing November & December 2020 in the chart. This vendor doesn't have any data for those months in the Capacity table, but I would expect the months to show on the chart.  Does it have something to do with how my data model is structured?

Data Model:

Line Chart output (the dotted line is just a constant):