Google improved search box within the search results not working

Question

I follow Google’s tutorial for improved search box withi

Answer 1

Looks correct (assuming that /search/site/strawberry successfully searches for "strawberry").

Note that Google is not displaying the Sitelinks Search Box for all sites/queries:

Search box not displaying? The sitelinks search box appears only for navigational queries and when relevant for users. Google algorithms use a variety of factors to determine when the box appears, including the information on the site and different types of navigational queries from Search users.

Edit: 2017-05-09 Updated Sitelinks Search Box Information and URL