way to recover FMG connection

One of our FGTs managed by FMG somehow lost connection to the FMG. It has two internet, wan1 and wan2. But probably when wan1 went down the FMG changed connection to wan2, then wan2 went down. Currently wan1 is up and operational, but somehow the central-management config has lost orignal config and had:

  config system central-management

     set type fortanalyzer

  end

So I changed it back to:

  config system central-management

    set type fortimanager

    set fmg x.x.x.x

  end

Then changed IP address at FMG under Device&Group->Edit Device to have this wan1 IP on the FMG side.

Based on my sniffing at the FGT, the FMG is trying to re-connect via this wan1 IP but the FGT seems to be ignoring the "SYN" packets from the FMG.

I know I can wipe out this FGT from the FMG and start over re-registering. But is there any easy way to just re-connect it?

By the way our FMG-VM is running v6.4.8 now.

Thanks,

Toshi