Memory card cannot read in Android phone

[AC Question]

I'm using Lenovo A850 Android OS, v4.2.2 (Jelly Bean) and mmc 8gb, suddenly i cannot read my mmc as usual.

 

[B. Diddy]

Welcome to Android Central! You're talking about an 8 GB external microSD card, right? Does it even show up in the Settings>Storage menu?

Try removing the card (Unmounting it first in the Settings>Storage​ menu, if you see the option), then insert it into your computer (using a fullsize SD adapter), and see if your computer can read it.