Hi. Just wanted share my experience with you in case there are people having the same problem and are stuck on figuring out what to do.
I purchased my Mazda3 s Touring over a month ago and ever since the infotainment system would occasionally not turn on after I started the car i.e. having a blank screen. The radio/volume control would still work but the screen was blank. Backup camera and Nav would not work because the screen was blank. Sometimes when I drove for 20mins it will turn itself on magically, but most of the time I would get stucked with a blank screen the whole trip and even the trips after. Tried changing every setting, reset to factory settings, upgraded the maps through Mazda tools. Nothing would work. I was on V27 and the car was manufactured in Feb 2014.
Frustrated and confused I started to look online for solutions, I came across a button combination that will restart the infotainment system and remembered it so that I can try the next time the screen won't turn on. It worked beautifully. After holding BACK + NAV + MUTE for 10 seconds the Mazda logo came on and everything is better
I've only used this trick three times and will see if it would keep working but I can't wait to share with other owners who might have similar issues. I know this is only a temporary/ghetto fix but it at least it let me have the backup camera and navigation whenever I need them.