Agent Client Collector is not able to push the policies to the Agent records from the instance.
You can see that by checking the Agents tab from the Policy record, as the following screenshot.
Paris Patch 1
If the instance got upgraded from Orlando to Paris Patch 1, this might be related to a CMDB known-issue: PRB1421666.
When upgrading from Orlando to Paris, some discovery_source values got deleted, including AgentClientCollector.
Export and import the sys_dictionary value for the discovery_source field from a newer release.
This known issue got fixed in Paris Patch 2 and newer.
If this didn't fix the issue, you might want to check the following KB which covers other Root Causes: KB0854460.