What if my device doesn’t allow the setup of passkeys because it’s managed by a third party (e.g., a company phone)?

It is possible that your device is managed by a third party (for example, if it’s a company phone), which may prevent the setup of passkeys. 
In this case, unfortunately, it isn’t possible to store a passkey, and you’ll need to use another device that supports passkey storage.
I don’t want to use biometric data for my passkey
Does setting the date/time affect the storage of my passkey?