Can't edit child theme's functions.php

It looks like something might be conflicting with Local on your machine.

Are you running other developer applications simultaneously? That could also cause similar issues. Apps like MAMP, XAMPP, or Docker for example.

Do you have any antivirus, security, or firewall applications that could be blocking Local? It looks like from the log it might be having trouble connecting.

More details about troubleshooting this here: Router Mode

You could also try changing your Router Mode to Localhost and then see if you can edit: Preferences>Advanced>Router Mode>Localhost