Upgrade to Ghost v4, but a lot of 503 error

Developer help
9

I did not configure special systemd, it’s default setting by Ghost:

[Unit]
Description=Ghost systemd service for blog: halfrost-com
Documentation=https://docs.ghost.org

[Service]
Type=simple
WorkingDirectory=/var/www/ghost
User=993
Environment="NODE_ENV=production"
ExecStart=/usr/local/bin/node /usr/local/bin/ghost run
Restart=always

[Install]
WantedBy=multi-user.target