Google decides which sponsored Maps format to show based on the campaign type, the user’s search or browsing context, location, relevance, and whether the business is eligible for that particular format. Google can show different formats, including Promoted Pins, Map Search Ads, Map Suggest Ads, and Placesheet Ads.
For example, a business may appear as a square Promoted Pin while someone is browsing the map, while a Map Search Ad can appear when the user searches for a specific service or business. Map Suggest Ads can appear in search suggestions before the customer finishes typing. The available format also depends on the campaign being used and the business's linked location assets.
So, you generally don't choose one Maps format and force Google to show it every time. Google determines the eligible format based on the user's context and the campaign setup. Auction competition can also affect whether your ad appears at all.