OK, now that I know what we're dealing with...let me ask some additional questions.
Are you a smoker? The residue from Smoking likes to settle on the keyboard contacts and can cause corrosion or prevent a reliable contact. It can be cleaned by removing and disassembling the keyboard and cleaning them with a warm dish-soap and water solution, rinsed, and air dryed. Note: This procedure is not recommended for those with less than an "expert" level computer of computer repair skill.
Does the Fn key action "feel" normal, or does it "feel" different than the other keys when you depress it? Dirt, food crumbs, hair, and other debris can get under the keycaps and prevent the keyswitch contacts from closing. Shut down the computer, disconnect the power supply and any peripherals, hold the laptop inverted, and blow out the debris with "canned air" and a soft bristle brush (like a small paint brush). Pay special attention to the keys that are not working, but try to get them all.
Do the F1-F10 keys work correctly as normal function keys (not the blue function) when used without the Fn key?
Or do they just malfunction only when used along with the Fn key?
Do the other keys in the column directly above and below the Fn key work correctly, or are they malfunctioning too?
Do the keys in the rows directly left and right of the Fn key work properly?
When keyboards fail, most often an entire column or row of keys stop working at the same time. This is due to the fact the the keyboard circuit is arranged as a matrix of crossing electrical pathways. Pushing a key closes the circuit path and causes the keyboard encoder to generate a key press.
If one or more of the column or row pathways has been damaged, or if the keyboard connector has become loose or been mis-alligned in it's connector, it can cause intermittent problems. Remove the keyboard and check the keyboard cable connection to the motherboard. Re-connect it if necessary.
As a last resort, the keyboard can be replaced with a new part from the manufacturer.
CptA
