Hey, I believe this issue has to do with a new formatting of Vimeo’s videos.
Vimeo does not allow Private videos to be embedded in 3rd party sites.
You can go through the Privacy Settings of Vimeo to better understand this.
Ref: https://vimeo.zendesk.com/hc/en-us/articles/224817847-Privacy-settings-overview
If you want to use your Vimeo video on 3rd party sites, you should use either Hide from Vimeo/Public settings or Vimeo will not allow these videos to be displayed.
If my earlier suggestion did not help, you can work around the issue completely.
Use another video source such as Youtube or self-hosting the video in your Media Library or Google drive.
Hope this helps (: