Are you given an option to explicitly set a thumbnail for your Vimeo video, on the native site? If so, I'd suggest doing that, then wholly re-inserting the video block and video link.
If the issue persists, then it means something isn't being communicated correctly between Vimeo's API and the URL reader used for the video block. In that regard, the best workaround would be to link an image of what you want for the thumbnail. Various 3rd party services can add play button overlays on the image, which you can then use in your email.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ William A Community & Social Media Support