Vimeo not working

Featured Video worked beautifully all the time, but suddenly the videos from Vimeo aren’t displayed anymore. I had that once already some time back (I posted about this here), but it eventually came back to work by itself. This is not happening for a few days here.

For example this post should show a vimeo video: https://c-opera.net/mathis-nitschke-viola-2015/
The video featured is this: https://vimeo.com/135171933
The error message reads: “Could not resolve the inserted value to a video. Are you sure it is a legal video url and the server can connect to its provider? If you tried to insert a raw embed code, you might need to enable it in the media settings.”
As you can see the video is in fact available.

Any idea?
Bests,
– mathis

The page I need help with: [log in to see the link]