If you receive the error message, "Security error: bad record message authentication code (MAC)," while trying to livestream, it means a secure connection could not be established. There are a few possible causes:
Incorrect Date / Time: If the date and/or time on your device isn't set properly, it can cause this error. Allowing your device to auto-detect the time for your area should prevent this from happening.
Third-Party Adapter: If you are using a third-party ethernet-to-lightning adapter, it could trigger the error. Try testing without the adapter to see if you still receive the error message.
Secure Packet Inspection: If you are using a public Wi-Fi network, it could have secure packet inspection. This means the network provider is injecting themselves between you and the destination server, which will cause security errors.