EventLog: Server TCP provider failed to listen on [ 'any' <ipv6> 1433]. Tcp port is already in use

This isn't a duplicate; my scenario is different from others I've found: https://dba.stackexchange.com/q/61923/63237 https://blogs.msdn.microsoft.com/sql_pfe_blog/2016/10/05/tcp-port-is-already-in-use/ https://support.plesk.com/hc/en-us/articles/213409409 Differences: - Neither cls & netstat -oanb -p tcp nor TCPView reveal anything listening on port 1433 - According to the EventLog message, this is occurring on IPV6 - The problem doesn't manifest for two named instances running on the same machine—only the default instance To my knowledge, I'm not using IPV6 in any way, shape or form. I certainly haven't configured it. The service will start when I make any of these configurations: - Disable TCP/IP in SQL Configuration Manager - Enable TCP/IP but turn off **Listen All** in **TCP/IP Properties** - When **Listen All** is off, disable all IPs on the **IP Addresses** tab If I do either of these, the service fails to start: - Turn on **Listen All** - Enable any IP address This has got me pulling my hair out. What's gone wrong here?