If you can not access your server, or your server appears down or unresponsive, I recommend checking your Cloud Firewall policies first. Confirm that the correct ports you are trying to access are added to your server’s Cloud Firewall. Then move on to the server firewall, networking, and application configuration next.
Checking Cloud Firewall
First, check out this guide on updating your IONOS Cloud Firewall:
https://www.ionos.com/help/server-cloud-infrastructure/firewall-policies/edit-a-firewall-policy/
If the ports exist and you still can’t reach your server, it’s possible that your servers internal firewall may be blocking you. It may also be the service isn’t running (for example, if Apache crashed, or Remote Desktop Connection is disabled), or that networking is misconfigured or disabled. It could also be a sign of something worse (for example malware or kernel panic).
Checking Internal Server Configuration
If you still can’t connect to the server, you should open up the remote console to take a look your server. Once connected to your server via remote console, you can investigate the server, including the firewall and networking.
Windows
Windows Server Firewall Documentation:
https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-firewall/best-practices-configuring
Check internet protocol properties of your server:
https://www.ionos.com/digitalguide/server/configuration/unidentified-network/#c492670
Linux
Ubuntu Firewall Documentation:
https://ubuntu.com/server/docs/security-firewall
CentOS / RedHat Firewall Documentation:
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/security_guide/sec-using_firewalls
Debian Firewall Documentation:
https://wiki.debian.org/DebianFirewall
Checking network settings (Linux):
https://www.ionos.com/help/index.php?id=4738
Monitoring server performance and check networking:
https://www.ionos.com/help/index.php?id=20757