Hi Liam Davis1,
I am Dave, I will help you with this.
The actions associated to the Function keys is controlled by the PC manufacturer, because the actions vary from PC to PC.
If a Function key is not working, try pressing the Fn key + a function key?
If it does, try pressing Fn + Esc to turn off the Function Lock.
If that does not solve the problem, check in BIOS if there is a setting to switch between Function and Media keys.
If not, click your Start Button, then just type msinfo and press Enter, please provide a screenshot of the resulting System Information window.