If I recall. 2014 models did not get the back up lines. They were using a different camera and screen system. It returned in 2015 with lines. Some early 2014 models may have gotten it . . not sure.
You might check the personal configuration settings to make sure.
2019 GMC Acadia SLT-1 3.6L LGX V6 - Build Date: 4-11-2019 - Bought 6-22-2019
SOLD - - 2015 Equinox LTZ 3.6L FWD Champagne Silver Metallic *Build Date 1-08-2015 *
SOLD with *38,865 miles 8-15-2019.