Your last fridge may have worked on that slope but it is to much for a rv fridge to work properly, also you need to check if you have a battery up to snuff as the fridge needs a good 12 volt source to work. Also you need to check all your fuses for the fridge again with the slope you have parked on, it may have blown a fuse?
Hope this helps and Happy Camping
2010 Cedar Creek Silverback 35ts
2001 GMC 2500HD w/ Allison & 8.1