I just got my three emails with daily flashcards, and currently had Russian as my active language at LingQ. I open each link in a new window, but all I got was Russian cards despite that two of them should have German and Chinese cards. In fact I saw the URL change from de/zh to ru. Is this a recent “invention”, a bug or what? I might be writing a forum post when the daily LingQs arrive, and don’t want to have to switch main language just to be able to go through the list…
This is a feature we added just for you, Jeff. 
Just kidding… We’ll try and fix it.
I have the same: the Spanish opened, but the Swedish and Russian ones don’t. Their links take me back to Spanish.
Progress? This time I saw my Russian flashcard, with the colours and header of Spanish. When I tried to do Swedish, Russian came back, again with the Spanish header.
For me, the right cards appeared after I changed language header (but until today I haven’t had to do that - the header has changed automatically according to the language of the daily flashcards).
Great! That way it works. I can now do my vocab. I love it when things get puzzled out. Thank you.
This issue with the LingQs of the Day has now been resolved. You no longer have to switch languages before clicking the link in the emails.