Start by getting one of these circuit testers:
About $5 at Walmart, Home Depot, etc.
Plug the tester into the garage outlet and see what it says.
Then plug your surge protector into the outlet and plug the tester into the surge protector and see what it says.
Then plug the extension cord into the surge protector and plug the tester into the extension cord and see what it says.
1988 Coleman Sequoia - popup (1987-2009) - outlasted 3 Dodge Grand Caravans!
2012 Roo19 - hybrid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado 1500 Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10