Had a similar problem, but it must be said that I was working with an external folder where I kept the file I was trying to get the icon to work on and kept the node_modules/react-native-vector-icons for it.

In my case the solution was adding some assets/fonts folders to myProject/android/app/src/main and put the MaterialCommunityIcons.ttf file from the myExternalFolder/node_modules/react-native-vector-icons folder.

Before that I had installed react-native-vector-icons on my actual project (which used the file from the external folder) but when I removed it (the react-native-vector-icons module) again the icons still worked.