The message 'Descoping Asset as respective agent status is unreachable' is just a warning message indicating that a previous job run (a CCS ping, CER job, Data collection job, etc) had a problem with the agent and it has been 'descoped' from future scans, and the descoping message is saying that the asset was skipped because that agent has known problems and has been marked 'red' in the Agent view in the console. Once the issue is resolved on the agent and it is verified by a CCS Ping (in the CCS Console) or running an Agent Management Job and the agent is marked 'green' in the Console, then that asset will be included in the next scan.
Release :CCS 12.5.x, 12.6
Component : CCS Agent
To see the actual error that is being reported when a scan is run on that agent, you can export a .csv file that will give details on what might be causing the issue.
First, check the 'available column' icon on the right hand side and enable all the columns:
After you enable all columns you click on the ellipse and select 'Export Agents to CSV'.
In the CSV, the 'Details' column will show the error that might help why the agent is not able to run scans or if it is not reachable, etc.
Using that information in the csv, you can also check to see if the following might not be causing the problem:
Handshake errors in CCS: