Post-migration, HBase hook for Atlas is not enabled by default on AM2CM migrated clusters. you must manually enable HBase hook.

To enable the Hive Metastore hook in your Cloudera Manager instance:
  1. Log in to your Cloudera Manager instance.
  2. Select the HBase service.
  3. Select Configurations tab.
  4. Search for Enable Atlas Hook that the HBase service depends on and check this.
  5. Click Save Changes.