Codes not working in custom theme

I'm working on a PIU theme for StepMania, and I can't get any codes to work in the Select Music screen. For example, I can't change the difficulty without going into the Player Options menu (the one you press Start twice to get to). So, if there are any experienced themers out there, I'm asking for your help please. I have provided a few snippets of the metrics below; let me know if you need any more in order to help me.

[CodeDetector]
Easier1=UpLeft
Easier2=MenuUp
Harder1=UpRight
Harder2=MenuDown

[ScreenSelectMusic]
Codes=CodeDetector

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