2056: Nothing readable.
The chat's unread messages cannot be marked as read.
HTTP status: 409.
A mark-as-read command was refused because every unread inbound message on this chat is of a type that cannot be marked read, such as a message type this API does not support. No read command was accepted. A chat with no unread inbound message at all answers nothing_unread instead.
Troubleshooting
Section titled “Troubleshooting”- Nothing is owed on these messages; send a read command again after the customer’s next supported message, which it will target.
- Read the chat’s transcript (GET /v1/chats/{chat}/events) to see which unread messages are unsupported.