Intro to CAD - Basic Features 1 Exercise - Can't Fillet some edges

I'm working my way through the "Intro to CAD" series in the Learning Center (https://www.onshape.com/learn/introduction-to-cad). I have completed Section 1, "Sketching" and was able to successfully complete the exercises.

In section 2, "Basic Features" I am having some trouble with filleting some the edges of the part as required in the exercise.



Here is my public doc:

https://cad.onshape.com/documents/56fb4904e4b0752611e72995/w/f0b0e92dc6e5cb6cacaf478c/e/7fba1e7473931e18ac8efece

I'm wondering if the way I created the features on the right side may have something to do with the filleting problem. Here is a screen shot that shows my method.