Thank you, @jota
I have checked the services, and they are running well in the machine.
php-fpm already running
apache already running
mysql already running
About the external IP configuration, I did follow the instructions to configure the external IP in Google, besides, there were some places different between the document and the layout in Google. However, something weird to me is that if I shutdown the VM or give it a new static external IP, the wordpress or phpmyadmin will be dead. I can't connect to them.
For example, I just started my machine 5 minutes ago, and I didn't configure the machine a static external IP, instead, I used the initial setting 'ephemeral IP'. According to the message in Deploy Manager in Google, the site address is:
Site address http://18.104.22.168/
Admin URL http://22.214.171.124/wp-admin/
But when you click the site address, you will get a new address in the browser http://126.96.36.199.xip.io/, and whole page is blank. I don't know why the address 188.8.131.52 will connect to 184.108.40.206.