Hi, Have you checked the power converter ? It has a switch for 12V/110V selection and likely a breaker or a fuse. Usually, there is also a 110V outlet directly on the power converter. Check with an electric tester for AC and DC voltage. The fridge
is connected to a 110V outlet accessible inside the RV fridge
trap. If there is no voltage there, your 110V breaker might need to be reset. If you connect your fridge directly to a 110V extension cord and select 110V, you can test the fridge to see if it works.
RV of that age often got modified in terms of electrical
system. You need to survey everything, find the components and check for connector and cables integrity, including under the floor.
By the way, blue wires can be the electric brake wire. If so, this is very bad news
Your RV needs position lights
and everything working to hit the road.