I receive the following message when attempting to capture a photo: The device must be oriented horizontally.
Rotate the device to the horizontal (aka: landscape, sideways) orientation.
Ensure the switch on the iPad is pushed up (in portrait orientation) or to the left (in landscape orientation).
Please note that this switch controls either the Mute functionality or the Lock Orientation functionality, depending on advanced iOS settings.
Check that Lock Orientation has not been set elsewhere. From the bottom of the screen, slide your finger upwards towards the centre -- this will open a settings menu. Depending on the iOS settings, you may see a lock icon near the centre-right of the settings menu -- ensure this button is NOT selected.
Please note that this icon may not be available, depending on advanced iOS settings. If this button is not present, you will see a Mute button.