Welcome to the forum.
The fuse and reversing the leads are the two leading causes of battery connection problems.
Also, if you did reverse the leads, then there are fuses that may have blown due to that condition. If so, just correctly connecting the leads may not fix your no power problem.
Sherm & Terry w/rescues Steve (std Poodle) & Eydie (min Schnauzer)
2015 Jay Flight 27RLS (Camped: 102 nights 2015, 90 nights 2016)
2006 Ford F350 6.0 PSD, Lariat, 4WD, CC, LB, SRW, auto., Camper pkg.