The management status of a firewall changes to Out of Syncstate when the firewall is locally modified. You need to synchronize firewall configuration with NSM to set the device in In Sync state.
To synchronize a firewall configuration with NSM
Review the configuration differences between NSM configuration and the local firewall configuration.

Review the pending commits.

Click OK in the dialog.
Synchronization process runs.
The firewall is now managed by NSM, thus the CONFIGURATION status changes to In Syncon the Manager View | Home > Firewalls > Inventory page.