Android - Marshmallow USB connection type
You can swipe down the Notificationbar and it will show Charging only. If you click that entry you can select the desired mode. The selected mode won't be set as default, so if you plug your device again, it will be on Charging only again.
To set the default mode you first need to enable developer mode (don't ask me why...). This can be done by going to About phone settings and clicking on the build number a few times.
Then go to the now accessible Developer Settings -> USB-Configuration (should be under the Network section). This should be set to the desired mode. In my case it was allready set to MTP (the desired mode), so i had to set it to another mode (for example Charge only) and then set it back to MTP.
Hope this helps!
EDIT: This only seems to work once. So if you disconnect and reconnect the device 2 or more time, the default is again on "Charge only". It is mentioned in the changelog of Android 6. Link-https://developer.android.com/about/versions/marshmallow/android-6.0-changes.html#behavior-usb
Go into Developer options, and cycle the USB host mode, the files will show up on my PC.
USB Mode: Set Default to MTP (file transfer) Marshmallow/6.0
Default is set to Charge only mode, You can enable developer options and enable MTP feature by following below steps:
- Settings -> About phone -> Touch 7 times on Build Number to enable Developer options
- Settings -> Developer Options -> Select USB Configuration -> MTP