Attempting to use yubikey fails: "could not get public key"

[cinerea0]

I know that yubikeys not set up with this tool aren't officially supported, but I thought this was odd. Here's the guide I used to set up my yubikey: https://github.com/drduh/YubiKey-Guide#creating-keys.

Output from yubikey-agent when attempting to use the yubikey:

2021/02/17 22:45:03 Connecting to the YubiKey...
2021/02/17 22:45:03 agent 11: could not get public key: command failed: smart card error 6a82: data object or application not found

Output of ykman info:

Device type: YubiKey 5 NFC
Serial number: 11417625
Firmware version: 5.2.4
Form factor: Keychain (USB-A)
Enabled USB interfaces: OTP+FIDO+CCID
NFC interface is enabled.

Applications	USB    	NFC
OTP     	Enabled	Enabled	
FIDO U2F	Enabled	Enabled	
OpenPGP 	Enabled	Enabled	
PIV     	Enabled	Enabled	
OATH    	Enabled	Enabled	
FIDO2   	Enabled	Enabled

[FiloSottile]

That guide uses the OpenPGP applet (except for bizzarrely making you change the PIV PUK, which I think is just a mistake in that guide), yubikey-agent uses the PIV applet. They don't share keys.