This issue can happen for a few reasons, most commonly due to improperly seated switches or switches that were damaged during installation.
Bent switch pins
Use the switch and keycap puller included in your packaging to remove the affected keycap and switch. Inspect the switch, if one or both of the copper pins are bent, gently straighten them using a pair of pliers. Once aligned, reinstall the switch and test the key again.
If the issue persists, we recommend bringing your keyboard down to our store for a more accurate diagnosis by our specialists.