When a rule is created and deployed using an in-memory enrichment and rows are later removed or added from the .CSV file, if the corresponding rule is deployed, alerts are not fired as expected.
This issue is fixed in the 10.6.2.0 release. If you are not able to upgrade to that release, please try the following workaround.
If rows are added to the .CSV file, remove the rule from deployment and deploy it again.
However, if rows are removed this solution does not work. In the case of removed rows, you can work around this issue by removing the existing enrichment source (via Alerts > Configure > Settings > Enrichment Sources) and uploading the updated .CSV file using a different name. Then, manually add the in-rule enrichment to the rule, and redeploy the rule.