The error message "Unable to start a scan. Error: Selected modules (iOS Bitcode) contain fatal errors" suggests that there might be issues with the iOS Bitcode in your build. Bitcode is an intermediate representation of compiled code used by Apple's App Store to optimize app delivery. Here are some steps you can take to troubleshoot and resolve this issue:

1. Review Build Settings: Check your Xcode project's build settings to ensure that Bitcode is enabled or disabled correctly according to your requirements. You can find this setting under "Build Settings" > "Build Options" > "Enable Bitcode".
2. Inspect Dependencies: If your project relies on third-party libraries or frameworks, make sure they are compatible with Bitcode. Some libraries might not support Bitcode, which can cause issues during the build process.
3. Update Dependencies: If any of your dependencies are outdated, consider updating them to the latest versions. Newer versions of libraries and frameworks often include fixes and improvements that can help resolve compatibility issues with Bitcode.