I think memrise made a switch to new servers (or something in that direction) this week.
Because I’ve noticed that the audio on the HSK courses are not served over https.
e.g. " http://static.memrise.com/uploads/audio/13110807185905_106837_a8be3.mp3 "
This is annoying when I force websites to use https and then in turn breaks the audio function on memrise.
Other courses I have checked don’t experience this problem.