Summary

If you create a lookup rule with complex logic that requires several fields to match database columns, an Auto-Fill button will appear on the form next to the last matched lookup field. The user must manually press this button to run the lookup.

Workaround

You can use JavaScript and CSS to hide the the Auto-Fill button and trigger the lookup when the user leaves any of the fields involved in the lookup rule. See this post on Laserfiche Answers for more information and code samples.