app not working in iphone and mac

My app when run on my mac by doing yarn start does not start. i get some error saying invariant violation, main has not been registered. (look at the attached screenshot)

Expo diagnostic info:


Expo CLI 3.22.3 environment info:
System:
OS: macOS 10.15.6
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 12.16.2 - /usr/local/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - /usr/local/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
IDEs:
Xcode: 11.6/11E708 - /usr/bin/xcodebuild
npmPackages:
expo: ^38.0.0 => 38.0.8
react: ~16.9.0 => 16.9.0
react-dom: ~16.9.0 => 16.9.0
react-native: ^0.61.4 => 0.61.5
react-native-web: ~0.11.7 => 0.11.7
npmGlobalPackages:
expo-cli: 3.22.3