Details
There is logic built into the Network Discovery to prevent a network scan that can potentially consume too many resources.
Steps to Remediate
Confirm that the network you want to scan is a large subnet of something smaller than a /17 (IE x.x.x.x/1-x.x.x.x/17). If the subnet range is within /1 -/17 you will need to change this scan from a subnet to an IP range
You will be able to use multiple network discovery inspectors to split the subnet you wish to scan
If you are unsure the range or how to break down a subnet, you will want to reach out to your network engineer