I have 2 mobile devices, a Samsung S7 phone and S2 Tablet.
Adding photos on the phone (S7) works properly AND at the top of the display the "Add From" location has a down arrow that allows me to choose the location to add from. HOWEVER, on the S2 tablet, I find two BIG differences:
1)at screen top add from location is missing the down arrow so I can't change the add from location, and
2) at the bottom only "Add Photos" is visible. On the phone I can choose either "Add Photos" or Camera
Both devices are running Android Marshmallow 6.0.1
Seems that there is a bug in handling the larger screen size on the tablet... things work perfectly on the phone.