# 50451: Only one identifier allowed for lookup: use either Identity or Address

Log Type: APPLICATION

Log Level: ERROR

## Description

This error occurs when your lookup request includes both `Identity` and `Address`. The participant conversation lookup supports exactly one of these parameters at a time.

### Possible causes

* Your request included both `Identity` and `Address` for the same lookup.
* Your request mixed a Chat user identifier with a non-Chat participant address in one query. Chat users are identified by `identity`, while non-Chat participants are looked up by `address`.

### Possible solutions

* Send only `Identity` when you look up conversations for a Chat user.
* Send only `Address` when you look up conversations for a non-Chat participant, such as an SMS or WhatsApp address.
* If you use `Address`, URL-encode the value before you send the request. For phone numbers, encode `+` as `%2B`.

#### Additional resources

* [Participant Conversation Resource](/docs/conversations-classic/api/participant-conversation-resource)
* [Twilio Conversations Overview](/docs/conversations-classic/overview)
* [User Identity and Access Tokens for Conversations](/docs/conversations-classic/identity)