Hello Nicholas,my name is Luiz Cruz independent consultant and I'm here to help you;
I understand that the media control on your Corsair KK70 keyboard is not working;
Do you have any previous keyboard drivers installed?
If so, I suggest you uninstall them completely;
Then download the CORSAIR iCUE v5.3 software from the link below:
https://www.corsair.com/us/en/s/downloads
Disclaimer: There are links to non-Microsoft websites. The pages appear to provide accurate and secure information. Watch out for ads on websites that may advertise products that are often classified as PUPs (Potentially Unwanted Products). Thoroughly research any product advertised on websites before deciding to download and install it.
Open the software and check the key assignments;
Set it up to your liking and check if it works;
Hope this helps, see you soon!