Parametric Search fields may be populated at walk time via the Data from Field settings on the All Walk Settings page. Each Parametric Search field was pre-configured at profile creation to accept data from the same-name meta data field, as a convenience. Alternatively, the field may be populated from other sources, such as the raw HTML, formatted text, URL, etc. Review the Data from Field settings and change as needed; see here. Make sure that every Parametric Search field is accounted for with a To Field, so that it will be populated at walk time. Changing the Rewalk Type to New may also be needed to ensure that newly-changed Data from Field settings take effect.