You can run a retrieve config on the device https://community.fortinet.com/t5/FortiManager/Troubleshooting-Tip-FortiGate-is-Out-of-sync-in-the-Device/ta-p/192888

To clear the pending changes from the FortiManager

Make the change in the FortiManager and see the Config Status change to Modified

Choose Install Wizard

Select the Device that needs updating

Get to Install Preparation Screen and Click Install Preview

If its trying to Purge VPN’s make sure you do this : ( Just clear out the comments from Phase1\Phase 2 and Static Routes ) https://community.fortinet.com/t5/FortiManager/Technical-Tip-Remove-comment-Created-by-IPSec-Template-from-VPN/ta-p/331346

This will show your changes that are being made to the device as other changes might have been made

Click Install only when you are ready to push the updates