SSH error on new install "GitLab: Failed to authorize your Git request: internal API unreachable"

This may be related to IPv6 support. On many Linux machines with IPv6 support, localhost resolves first to ::1 (IPv6), so you may not be able to reach a service that is only listening on 127.0.0.1 IPv4.

You can run netstat -ltn | grep 8080 to see whether it is listening on IPv4, IPv6, or both.