When search returns nothing, or the box itself is missing, the cause is almost always one of four things: an inactive license, an empty or stale index, a post type outside the scope, or a query shorter than the minimum. Work through them in that order.
If the search box is missing entirely, the license is the first suspect: without an active license the shortcode and Breakdance element render nothing for visitors, and administrators see a “License is not active” notice instead. Activate it under Elevated › Site Search › License.
Go to Elevated › Site Search › Settings › Advanced Options › Indexer and read the status line. It should name the active engine, a recent rebuild time, and a plausible document count. Anything else, click Force Index Rebuild.

Only indexed post types return results; posts and pages are the default. If products, docs, or another type should be findable, add them under Content to Index (see Choosing Which Post Types Get Searched). Drafts and private content never appear.
The box starts searching at three typed characters by default (Minimum Characters under Theme & Style › General Controls). Two-letter queries return nothing until that threshold is lowered.
If your agent is connected (see Connect Your AI Agent), you can skip the steps above:
Site search returns no results. Check the index health, the document count, and which post types are indexed, and tell me what's wrong.
The agent reads the health check, the index status, and the scope in one pass and reports the mismatch.