Active/Standby, failover unable to contact firewall


I have a pair og SG650 in Active/Standby, the Master works perfectly, but if I initiate a failover to the slave, either via a takeover from CLI or a reboot of the primary etc. I am unable to contact the new primary (previous slave) via Eth1.

Both devices are connected to from Eth1 into a single switch which has the most basic config on those corresponding interfaces. They're both in the same vlan.

I've updated the devices to the latest fitmware, but didn't expect that to resolve the issue.

It's as if the slave never picks up the primary's IP address.

I'm pretty new to the Sophos lineup, but know CISCO ASA failover config really well, I figured it's be similar whereby the secondary/slave unit takes over the primary address, but in this instance this doesn't seem to be occuring.

Any ideas as to what the cause could be? I've ruled out faulty NIC's on the switch.