Start pulling stuff away from the walls and check all GFCI outlets. Also go walk outside and check GFCI outlets. Sometimes you will find a Kitchen, Bath, Crawlspace, Basement GFCI controlling the Garage, depending on who did the wiring.
Hopefully you cut a hole for that or moved the shelves. Since they are movable, you may want to put a blank in and just put a GFCI breaker in, if you are limited where that shelving unit can go. Otherwise cutting a hole in the back will give you access to that outlet.Thanks for your help. I did find a tripped GFI. It was hidden behind some wall to ceiling shelves. Problem solved.