Did you enable 'Private Mode' in Privacy?
Settings > privacy & emergency > private mode > private mode (toggle ON)
OR, access it from the notification shade dropdown
pull down from top of the phone > scroll the action tiles until you see the 'Private Mode' tile, and toggle it on.
Once either of these is accomplished, the Private content will be visible.
Open Gallery > find the 'Private' folder...all the private photos will be visible in it.