Pretty uninformative rating but not a surprise based on your own rating history. Tens of thousands of users have been able to use the plugin with out “fail” in fact.
We HIGHLY doubt you followed the directions, especially since a basic embed should at least appear even without our plugin installed ( http://codex.wordpress.org/Embeds ). You wouldn’t get any of the customizations that our plugin provides, but a basic video would be playable.
The only suggestion here is to always follow these rules (mentioned in many places) when pasting a link:
Make sure the url is really on its own line by itself.
Make sure the url is not an active hyperlink (i.e., it should just be plain text). Otherwise, highlight the url and click the “unlink” button in your editor.
Make sure you did not format or align the url in any way. If your url still appears in your actual post instead of a video, highlight it and click the “remove formatting” button (formatting can be invisible sometimes).
Finally, there’s a slight chance your custom theme is the issue, if you have one. To know for sure, we suggest temporarily switching to one of the default WordPress themes (e.g., “Twenty Thirteen”) just to see if your video does appear. If it suddenly works, then your custom theme is the issue. You can switch back when done testing.