DroboShare uses SMB over TCP, so you need port 445 open.
If you want Drobo Dashboard to be able to connect through a firewall the easiest way is to put Drobo Dashboard in the firewalls’ allowed-programs list.
If your firewall doesn’t offer a feature with an allowed-programs list, you need to open ports 5000 and 1024-65536. Drobo Dashboard connects to port 5000 and then randomly picks a port in the range for broadcasting.
Just one quick note. No other software have created so much network-related work for me during the years as zone-alarm. Previously it even blocked ports when it was disabled, didn’t disengage port 63 block until it was uninstalled. I think that is resolved in newer versions.
My recommendation is always to just go with the built in firewall and use a stand-alone router with firewall.