Try below given solutions:
- Take your external memory card off your Android smartphone or tablet. Make sure that your device is turned off as you do this.
Use a white colored rubber eraser to rub the copper piece (gold yellow color) on your MicroSD card.
Once you’re quite sure it’s clean, plug it back into the memory slot and then turn your android smartphone or tablet on. - Open the ‘Settings’ app on your device and then go to Storage.
Find the ‘Erase SD card’ option and tap on it. This deletes all data and makes it look like a new memory. - Connect your Android device to a PC or laptop via the USB cable.
Ensure that the device is connected as MSC (Mass storage mode), not MTP (Media transfer mode).
Launch windows explore on your PC and right click on the MicroSD card driver. In the options that appear, choose Properties>Tools>Error Checking. Wait for the process to complete.
After completion, eject your SD card and put it back into the memory slot on your phone or tablet. Check whether it works.
Above solutions are sufficent to solve your issue but if it get fails then check Motorola Nexus 6 Manual for more methods.
