Hi Wads,
Please note that extra keys on a keyboard such as F20 - F24 are not usually within Narrator's scope. Meaning it wasn't program with those keys in mind. For further assistance with this issue, I highly recommend getting in contact with our Disability Answer Desk support as they have more technicality about Narrator and how you can maximize using them. You can contact them through this link. For now, I suggest using Caps Lock + 1 to be enable to turn on input learning. This will let Narrator echo the name of the key and its associated command.
Let me know if there's anything else you need.