Important: The parameter name is case-sensitive and must be userId (with capital "I"), not userid.

The error you're seeing occurs when the parameter is lowercase userid instead of the correct camelCase userId. Using the correct casing will return a list of all identity provider IDs that the user is currently linked to.

Make sure your request looks like:

This endpoint works with a standard API key and will return the identity provider link information you need to determine if a user is linked to external providers.