The telephony user credentials endpoint returns 401 Unauthorized when migrating from Zendesk Talk. The token expires immediately after generation, unlike the persistent sessions in Zendesk.
telephony:readThe 401 error typically stems from mismatched OAuth token lifecycles rather than scope issues. Genesys Cloud access tokens default to a 24-hour TTL, but refresh tokens require explicit offline_access scope to persist beyond that window. Ensure the client ID generating the token has the offline_access scope enabled in the admin portal under Organization > OAuth Clients. Without this, the access token expires, and subsequent calls to retrieve user credentials fail because the session is no longer valid. Also verify the JWT signature matches the registered public key in your integration settings. If using a service account, check that the user associated with the token still has the Telephony User role assigned. Revoking and re-authorizing the app often clears stale token caches that cause immediate expiration upon generation.