An RV refrigerator will take anywhere from 8 to 24 hours to get cold and for things to freeze in the freezer. Some seem to be a little faster at chilling down than others. Ambient heat around the camper can make the initial cool down slower too. Once cool, they stay cool. But the initial cool down takes several hours. That's why we leave ours turned on 24x7x365. We use it too much to turn off and wait for cool down to happen again.
Be patient. Give it 24 hours. Set a cup of water in the freezer section. See if it freezes after 24 hours.