I have a fresh install of Discourse and try to add a Passkey to my user. Unfortunately I get this error:
Any ideas why this could happen? I have not changed any settings.
AI-generated summary
SaraMiller encountered a passkey error while trying to add a passkey to their Discourse user account on a fresh installation. The issue occurred on their MacBook Air but not on their Mac Mini, despite both devices using the same iCloud Keychain. After syncing the passkey from the Mac Mini to the Air and attempting to create a new passkey, the problem resolved itself, with a 502 error on the first attempt but success on the second. The issue may have been related to a macOS update (15.4.1). The user confirmed the passkey worked on other platforms, including meta.discourse.org, and the problem is now resolved.
I am trying to do it for my own user (who is also the only user and the admin user).
Can you register your passkey on https://webauthn.io/ and use it to log in there?
That will help determine whether the problem is related to your client system or your installation.
Does it work on this site?
Yes it does, as show in the picture. Or am I misunderstanding something?
Is your site on https? When you see this error, you can also open the javascript console of your browser, it may have some more information.
Ok, the strangest thing just happened. I am now on my macMini and it just works. I did not work on my MB Air.
Will try to update my Air to 15.4.1 and see if the problem is gone.
Yes, my site is https and NGXIN redirects HTTP.
I meant on this site, as in meta.discourse.org 
haha, yes. Here it also worked with my Air.
Ok, back at my Air, the passkey from my mini synced over iCloud to my Air.
And I can login in with the Air over passkey.
So I deleted the passkey again.
And tried to create a new one. Which worked 
I got an 502 error the first time I clicked on “Add passkey” but it worked the second time.
So I don’t know what really caused this, maybe the update on my Air to 15.4.1.
Either way, the problem is solved for me 