SWQL query that has stopped working

SELECT DATETRUNC('DAY', AT.LastDiscovery) as [DateLastDiscovery], count(LastDiscovery) as DateCount

FROM NCM.ArpTables AT

group by DATETRUNC('DAY', AT.LastDiscovery)

order by DateLastDiscovery DESC

The last time this produced data was 12/1/2020.  Just wondering if the community has any thoughts as to why it stopped showing data.