What make/model of computer do you have?
Open a terminal window and run:
A window will popup on your screen. Press your Fn+F1 key combination, and hopefully something will display in the original terminal window related to a keycode value. e.g.:
Post back the results.
state 0x0, keycode 235 (keysym 0x1008ff59, XF86Display), same_screen YES,
If you get a keycode returned, you can try to manually initiate the action via:
This code can then be added to your startup scripts.
sudo acpi_fakekey <keycode>