The Export Map functionality of ArcGIS for Server returns a blank image if using the timestamp function to query a DATE column in the Layer Definitions box.
Duplicate of BUG-000166180.
The fix is also released as a patch for ArcGIS Server 11.3. Refer to the documentation for more information: https://support.esri.com/en-us/patches-updates/2025/arcgis-server-11-3-map-services-definition-query-patch