What happens when a required placement is unavailable in the ad server during the check...

When a required placement is unavailable in the ad server during the check availability process with Google Ad Manager, a red check mark appears in the availability column (D). This clear visual cue signals to the user that the desired placement is not available, prompting them to consider alternative placements or adjust their campaign strategy accordingly.References:

https://help.salesforce.com/articleView?id=sf.dmp_advertising_sales_check_availability.htm

https://www.salesforce.com/products/media-cloud/overview/