The font embedding process can succeed completely or fail, depending on the presentation file you chose and on the fonts it uses.
When the embedding process succeeds, a green circle with a check mark will appear on the presentation thumbnail. This means that all fonts have been embedded and that a new presentation file containing the embedded fonts has been created. Clicking the linked filename will open a new Explorer window and select the new file.
In cases where the fonts could be embedded (e.g. the app could not find or communicate with Microsoft® PowerPoint®, the file was read-only, other error, or etc.), a red circle with an X mark will appear on the presentation thumbnail.
The main title of the window will provide you with information for the failure.