...
When asked to sing in with your passkey select the option "Security Key", then click 
;
You are now notified that access to google will be prepared with your Fido2 security key - click 
to proceed to the next stepYou will now be asked to touch the Fido2 key (in the case of a Fido key with a fingerprint reader you will need to swipe your finger on the key);
Once the key has been touched you will be logged in to your Atlassian account.