"a) Ask the customer to open the phone's camera app first and then scroll Up/Down on the case to click a photo

b) Check if the phone's own volume buttons click a photo in the camera app. If not, enable it from the camera settings (e.g. Camera settings > Shooting methods / Volume key function > Take pictures/Shutter - menu name may vary by phone brand)

c) If the camera zooms or the volume changes instead of clicking, the volume key function is set to Zoom/Volume in the camera settings - change it to Take pictures/Shutter

d) If photos are getting clicked accidentally, educate the customer that the scroll works as camera shutter while the camera app is open - avoid touching the scroll while the camera is open

e) Third party apps (Instagram, Snapchat etc.) may not support volume button shutter - use the phone's default camera app

f) If the scroll changes the volume normally but does not click photos, it is a phone/app setting issue