This issue happens in react-native-firebase for a various reasons.
First thing you have to do is check
- Firebase/Core is in your pods.
- Try Cleaning and rebuilding your project.
- Click on the target you are running in xcode and check the frameworks section in ‘General’ Tab -> Check you have linked libFirebase.a there. If not click the “+” button at the bottom and
add it. if you are not finding it, then right click the project -> Add Files to Project -> Add
and link the project.
- Comment use_frameworks! in your pods file.
- If above is not working for you, then try these commands in terminal
rm -rf ~/Library/Caches/CocoaPods;
rm -rf Pods;
rm -rf ~/Library/Developer/Xcode/DerivedData/*;