By default, Cloud VPS comes with preinstalled CentOS6, so you need to recreate it with CentOS7. Please look here for detailed instructions.
After recreating the server, you will have to change firewall settings.
1. Connect to your server via SSH (using e.g. Tera Term terminal).
2. Open ports 8443, 8447, 8880 used to connect to Plesk by entering the below command:
# iptables -I INPUT 5 -p tcp -m multiport --dports 8443,8447,8880 -j ACCEPT
With the above command rules to open ports 8443, 8447, 8880 will be inserted as 5th. You can choose where to put it in the rules chain by changing bold 5 to appropriate number. You can see current iptables settings with
# iptables -S command.
3. When finished, save setting with
# service iptables save
4. Last, confirm if you are able to connect to Plesk.
Please see here for details about accessing Plesk for the first time.