Why might my F6 (assigned to a style) suddenly stop working?

UPDATE: I restarted my computer and the F6 assignment key disappeared from my Mac Settings. I recreated it, and it’s working on Scrivener again. (Feel free to delete this post.)

I have a series of styles assigned to my F keys. Curiously, just one of them has stopped working!

What preceded this? As far as I can tell, nothing relevant. One thing I recently did was choose to “Show Format Bar” and “Show Ruler” (to fix some bad styling imported from a copy-paste). Then I hid them again.

Things I’ve done to diagnose:
• Checked the F6 key works
• Checked the style name matches the name in the Mac keyboard settings (assigned to F6)
• Checked that the style itself works (when manually clicking it in the style pane)

Any other tests I could run? Thanks!