If you are using a USB hub, extension, etc., check whether inserting the key directly into your computer makes a difference.

Linux users check lsusb -v in Terminal.macOS users check (Apple Menu) > About This Mac > System Report, and look under Hardware > USB.Windows users check Settings > Devices > Bluetooth & other devices.The YubiKey Bio will appear here as YubiKey FIDO, and blue Security Keys will show as Security Key by Yubico. Make sure YubiKey OTP+FIDO+CCID or similar appears in one of the following locations when the key is inserted.Additional troubleshooting steps for the YubiKey Bio can also be found on this page under Frequently asked questions (near the bottom).For YubiKey Bios, make sure you have enrolled at least one fingerprint - see this page for initial setup instructions.See here for a visual example of how the YubiKey 5 Nano looks when properly inserted into a USB port. If it doesn't, try flipping the key over and inserting again some USB ports are upside down.

Plug in the key and check whether the LED turns on.For help identifying your YubiKey, see Identifying Your YubiKey. If you are having trouble using your YubiKey (including YubiKey Bio) or Security Key, follow the troubleshooting steps below.

Usbc yubikey