I have a LG Nexus 5 with android marshmallow OS. I used to be able to connect my phone to a PC running Windows 10 with USB cable and browse the files from the PC's file explorer. Ever since I upgraded the OS to marshmallow whenever I connect the phone to PC with USB cable, the PC detects the connected phone but when I open the phone from file explorer there is nothing shown.
After a lot of exploration I found a setting in the notification area called 'USB for charging. Touch for more options'. From there I can choose charging only, MTP, PTP, or MIDI. After selecting MTP I can browse the phone content from PC. This setting used to be in Settings - Storage - USB computer connection.
The problem is the next time the phone is connected to the PC, the setting revert back to 'charging only'.
Can I set the default to MTP like it used to be in lollipop?