Schema is valid but no rich result is showing
Your markup passes every test and the search result still looks exactly the same as before.
Eligibility is not display
Passing validation means your markup is well-formed and complete enough to be considered. Whether a rich result appears is decided per query, per result, at serve time, and is frequently withheld from perfectly valid markup.
Check the required properties, not just validity
Each type has properties that are required for rich-result eligibility and others that are merely recommended. A block can be entirely valid and still miss a required field, which is a silent disqualification.
And check it is actually in the served HTML
If your schema is injected by JavaScript after load, the crawler may never see it. View source, not developer tools: the inspector shows the DOM after scripts run, which is not what was served.
Valid is not the same as eligible
The Rich Results Test will happily tell you the markup is valid while Google declines to show anything. Validity is the floor. Above it sit eligibility rules per type, quality thresholds, and Google's own judgement about whether the enhancement helps this query. A green tick is confirmation you did not make a mistake, not a promise of a rich result.
Check what the crawler receives
View source, not inspect element. Inspect element shows you the page after JavaScript has run, which is not necessarily what was indexed. If the JSON-LD is missing from view source, that is the answer, and it is a build problem rather than a schema problem. This is the most common cause and the fastest one to rule out.
Measured, not asserted
On a scan of this site, every one of 22 types parsed cleanly. Parsing cleanly is the floor, not the goal, and it is where most schema advice stops.
Free tool for this: Schema Inventory. No account, nothing uploaded.
Where this goes deeper
Every number on this page comes from one complete dataset: one product taken from zero to 100K+ users on search alone, with nothing spent on advertising. The full argument is Chapter 7 of the book. Five chapters are free to read.