I recently upgraded my phone to android lolipop with cm 12 while doing so i first cleared all the data and also deleted my partition, now after installing lolipop i Can't access my internal storage on d phone but I can see it in the file manager .Next when i download apps from play store an error shows insufficient storage available, but I have ample space on my device,internal SD and ext sd. And when I tried to create a SD card partion via cwm 6.0.5 , the option of SD partion was not there in advanced option.please help I have a Samsung galaxy note n 7000
You may need to change the USB settings on your phone. I found the answer here.
After you connect your Nexus to your PC/Mac via USB, swipe down on the Notification shade, and select MTP there from the USB options shown.