Set the new DHCP subnet and gateway on the hub and save it. Then set the IP address of the machine you intend connecting to the hub manually within the new subnet. Then see if you can connect to the hub. If you can, restore the machine back to obtaining address automatically and see if it is served an address in the new subnet.
@ShedDriver Yes. The issue was just that the range set in the DHCP must be valid for the address set on the SH2 even when the DHCP is subsequently turned off in favour of a different DCHP and that it does not report this as an error. It just reverts back when saved. The point may be irrelevant if you are using the DHCP on the hub.
Also note, if you change the subnet, the machine you are connecting from will disconnect. As Licquorice says, while setting it up, using a static address in the correct range on the connecting PC is the easiest way to go. Even then it will need a manual change to keep up with the change to the hub when it restarts. Once everything is working you can put the PC back on automatic.