The results point out to this keyboard : https://nos.gg/nos-c-450-mini-keyboard-pro-cott...
If it is the correct one the keyboard does not have a fn lock feature.
Try pressing and holding fn key + the space bar key for around 3 seconds. Check if this factory resets the keyboard.
Disclaimer: this is a non Microsoft website. The page appears to be providing accurate and safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (potentially unwanted products). Thoroughly research any product advertised on the site before you decide to download and install it