Even if it works for a short time, it can be a bad card. (And if it's not a SanDisk, getting it replaces is a game of Russian Roulette. If it is, go to
SanDisk microSD Tech Support - live chat. They're pretty good at figuring out how to fix the card, or getting you set up to get a replacement.)
BTW, Android was never designed to run apps from the SD card. The fact that it can just happens to be an accident, not a design feature. You really shouldn't be moving any apps to it. (And moving apps to the SD card doesn't really save that much space for most apps. It depends on how the app is written and, since "moving to SD" isn't part of Android design, most people don't even check to see if their app can run when moved. But if it's written in a lot of small pieces, moving it can actually cost more internal space than you save. [Pointers are left in internal storage for each piece moved - if the piece is smaller than a pointer, it leaves you with less free space to move the app.])