[Bug]: WebAuthn passwordless login not working although set-up

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I have set up a Nitrokey 3C security key for my user in a managed Nextcloud instance for passwordless login in my users settings in the "security" section. The setup worked and the key is shown with the name I have given it.

However, when I try to login without a password by selecting "login with a device" on the login screen after entering my account mail address Nextcloud is telling me "Your account is not set up for passwordless login". (please note: the nextcloud instance is in German and I cannot change it so the wording might be slightly different).

Also, I didn't find any information about this particular error message or passwordless login in general in the official documentation so I don't know if I might have to set up anything else to make it work.

Steps to reproduce

1. Set up a Nitrokey 3C as security key for passwordless login
2. Logout and go to the login page
3. Select "login with a device"
4. Enter account mail address
5. Confirm

Expected behavior

Nextcloud should start passwordless authentication and make Firefox ask me to touch my key to login.

Installation method

None

Nextcloud Server version

25

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

Since this is a Managed instance where I only have a regular user account I cannot get additional information besides Nextcloud version which is 25.0.7.1

No files or tests are named. Start with the reported login flow: register a Nitrokey 3C in the Security settings, then use “login with a device” in Firefox on Nextcloud 25.0.7.1 and trace why the registered key is rejected. Done means the passwordless flow recognizes the key and prompts for a touch.