Automatic keyword capture applies to eligible campaign replies, not every incoming chat. The configured keyword must match as a whole keyword and the reply must meet the campaign's eligibility window. A message containing unrelated text is not necessarily the configured response.
Check that capture is enabled and compare the reply time, campaign reference, and suppression source. Preserve the customer's preference while investigating; missing automation is not permission to send. Give support a redacted example and the displayed result. Do not remove an opt-out merely because the automatic capture did not run.