am using clickhouse query in Dashboard panel

SELECT
    now() as ts,
    stringTagMap['messaging.destination.name'] as `messaging.destination.name`,
    resourceTagsMap['service.name'] as `service.name`,
    toFloat64(count()) as value
FROM
    signoz_traces.distributed_signoz_index_v2
WHERE
    (timestamp >= {{.start_datetime}} AND timestamp <= {{.end_datetime}}) 
    AND stringTagMap['messaging.system'] = 'kafka'
    AND (resourceTagsMap['service.name'] = {{.region}} AND resourceTagsMap['service.name'] LIKE '%IND%')
    AND stringTagMap['messaging.operation'] = 'publish'
    AND has(stringTagMap, 'messaging.destination.name')
    AND has(resourceTagsMap, 'service.name')
GROUP BY
    `messaging.destination.name`, `service.name`

{{.region}}. is not getting populated this is showing no value in the query service logs even when i pass the region in the Dashboard variable

What does the request payload look like?