Internal storage not mounting on all Android M ROMs I have a problem with my HTC Desire 816G (MT6592). Whenever I install the Android M ROM, internal storage doesn't mount. My phone's internal storage doesn't appear in USB mode and nor in file manager. The phone's features like Gallery, Camera, Recording, etc., are not working on all Marshmallow ROMs. Lollipop and Kit Kat work fine. I didn't have this problem with Marshmallow ROMs before. I've been stuck for around 2 weeks now.
Try to format internal storage with /system, /data, /cache. Do these format with recovery, whatever you are using. 

Do it multiple times until all of them get mounted and internal storage shows your space. 

Two days before on my new rom flashing I got hell out of that situation by doing so as written above.