Clear both the cache and data from the "Download" app and the "Download manager" app.
Settings–>Apps–>Download–>clear cache–>clear data
Settings–>Apps–>Download Manager–>clear cache–>clear data
For some reason, this has to be done on my girlfriends MX5e every now and again for it to start downloading. Seems to be a problem with data not wiping itself after X amount of downloads. I’ve has a few Meizu phones in my time but only have had this problem on hers.