Looks like the 1.23.3 BIOS update for the E7470 released on June 18th broke the mic input LED on the F4 key. I confirmed this by rolling back to the previous version (1.22.8) and the issue wasn't present. If the LED was turned off before updating the BIOS, it will never get turned on again despite the function working as intended (muting and unmuting mic input). If the LED was turned on before updating the BIOS, again, it will be impossible to turn it off despite the functionality not being affected by this.
Solved! Go to Solution.