B800i stopped working off subnet


We have a Drobo B800i that is connected to a Windows 2008 server through iSCSI.
It has been working great for a few years.
Last night, it restarted.
After the restart, it will not allow communication from anything off subnet.
From a computer on the same subnet, I can ping, use the Drobo dashboard, see it in the Windows iSCSI Initiator interface.
From the server it has been connected to, I can’t get it to respond in any way.
Other devices on the same subnet as the Drobo can be reached from the server.
Firewall rules have been checked and tested. I can’t find anywhere on the Drobo Dashboard to change an ACL or similar settings.
Network, IP, Subnet Mask and Gateways are correct.

Does anyone have any theories as to why it would suddnely stop working across subnets.