自己想出来。怀疑，这确实与防火墙有关。
在GCE实例中允许HTTPS流量时，默认端口为443而不是8443.
更改侦听端口或更改防火墙规则：

Figured it out myself. As suspected, this does have something to do with firewall. When allowing HTTPS traffic in a GCE instance, the default port is 443 not 8443. Either change the listening port or change the firewall rule here:

Google Developers Console-> Compute Engine-> Networks->该实例所关联的网络
名称 - >防火墙规则。

Google Developers Console->Compute Engine->Networks->the network's name the instance is associated with->Firewall rules.

列出了几条规则，在我的情况下我需要修改 default-allow-https

Several rules are listed, in my case I need to modify default-allow-https