Hello @Preston,
After looking at the PBIX I managed to activate the sorting option that was not visible in your case. But the thing is if your try to do/apply the sorting in your “Line and Stacked Column Chart” it won’t provide you the desired results that you’re trying to achieve. Below are the steps mentioned alongwith the screenshots provided for the reference -
Step 1: Sort By option not visible in the chart.
Step 2: In order to activate the “Sort By” option. Go to the Format tab and under that “X-Axis” option, change the “Type” from “Continuous” to “Categorical”.
Step 3: Now, you can check under the 3 dots ellipses that “Sort By” option is activated. (Note: Observe the months on the X-Axis by comparing it with screenshot No.1)
Step 4: Now, if you try to sort them by “Dollars” in “Descending Order”. You would expect that individual bars would be sorted from Descending to Ascending but rather than doing the sorting in that manner it will actually sort the months from highest to lowest by comparing the dollars over a period of time. Below is the screenshot of the end result provided for the reference -
Conclusion: The Bar Chart will sort the X-axis rather than sorting the categories that contains within the individual line items.
I’m also attaching the working of the PBIX file for the reference. And also providing a link below where similar sort of query was asked onto the Power BI Community Forum where no solution is available for it yet.
My apologies but I guess this is as of now one of the limitations in the Power BI.
Hoping you find this useful. 
Thanks and Warm Regards,
Harsh
Salesbyproductline.pbix (1.4 MB)