Dropped vehicle off at a shop to replace my side mirrors on my 2019 Blazer Premier. All of the cameras work perfect including the side cameras on the mirror for the 360 degree view. Now the guidelines are gone and don't show up even with it enabled and a timer appeared in the top left.. I tried resetting everything to factory setting within the system and no change.

 

Issue went away; not sure if it just takes 24 hours for the cameras to settle in your calibrate or whatever they're doing but the timer went away and the guidelines are back.