IPSec VPN with Failover WAN

I have two FG61Fs running 7.4.6 with a Dial-Up IPSec VPN between them.  I recently added a second WAN connection for failover purposes.  I use the link monitor to kill the static route with higher priority when my primary goes down.  That works great.

For the VPN, I added a second tunnel bound to the backup WAN interface.  Both IPSec interfaces are in a zone, and I use the zone in the policies.  I cloned the static route from the original tunnel and changed the interface to the new backup tunnel and gave it a greater priority value than the original.

The screenshot below shows the remote side.  This is what I see when on my primary WAN.  If I unplug the primary WAN at the home office, the HomeOfficeTMO (backup) tunnel Phase 2 comes up - but I can't pass any traffic over it.  If I manually disable the Static Route for the primary WAN tunnel on the Home Office, it starts to work.  I thought that if the primary WAN tunnel was down that would take the route down.

Do I need to put a monitor on that?  Or is there a better approach to this?

Thanks!