Bug Report!
The code you posted doesn't appear to be complete. The closing /nabble_embed tag is not all there - although that might be because you did not enclose the tag in "raw" tags.
However, there does appear to be a bug in Nabble code or documentation as enclosing the code provided by Vimeo in nabble_embed tags does not run the video. It just shows the code!
The work around is to check the box "Message is in HTML format" and use only the code provided by vimeo (i.e. do NOT use the nabble_embed tags). However, that does mean that you need to wrap every other part of the message in appropriate HTML tags
Daily workout 10/15/14 from Primetime on Vimeo.
Click Reply and then use the "Quote" button to see the HTML code I have used to write this message.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.