45211: Provided identity is reserved by system

This error occurs when you create a Flex Chat Channel and the required identity value is one that the system reserves for internal use. The identity parameter uniquely identifies the chat user for the new channel, so you must send your own valid user identity in the request.

• You sent a reserved value in the identity field while creating a channel with POST /Channels.
• Your channel creation logic is assigning a system-reserved identity instead of a unique identity for the chat user. Flex requires identity for channel creation, and custom chat integrations also rely on a unique user identity.
• Your application is reusing an identity value that is not intended for customer identities in Flex messaging. Flex Flows connect messaging identities to Flex, and the channel request must provide a valid chat user identity.

• Change the identity value in your request to a different valid identity and try again.
• Make sure the identity you send uniquely identifies the chat user for the channel you are creating.
• If you use a custom chat integration, generate identities from your own customer or application user IDs instead of hardcoded system-style values.
• Do not use PII such as a phone number or email address as a custom chat identity. Use a stable application identifier instead.
• Review the code that creates the Flex channel and confirm it sends the correct flexFlowSid and a valid non-reserved identity for the user.

• Flex Chat Channel Resource
• Manage Flex Flows
• Integrate a Custom Chat Client with Flex