Why did a network scan not find any alive/active hosts?

The most common reason for this issue is that the scan profile used did not have the correct settings to discover hosts or the firewall was not configured correctly.

Every scanned network requires different scan discovery techniques to adapt to how the network is configured. TCP SYN detection is usually the most used detection technique, while sometimes you need to utilize SYN+ACK or even ICMP with different combinations.

It is recommended to start tuning the scan profile first with a smaller set of hosts scanned to ensure it is accurately discovered before checking more extensive networks. 

Read more about different scan techniques:
https://support.holmsecurity.com/knowledge/how-does-the-network-discovery-work

When performing a scan on a local network using a Scanner Appliance, verifying that it can effectively communicate with the target hosts is crucial, mainly when deployed in a separate subnetwork. This ensures that the scan can accurately discover and scan the hosts within the network.

Read more about firewall settings for the Scanner Appliance here:
https://support.holmsecurity.com/knowledge/what-are-the-firewall-settings-for-scanner-appliance