@Hank21 

Thanks for your advice.

I have set the default gateways.

After studying the specifications of the L2+ switch, I have found that this switch does not support IP forwarding.

So I gave up setting the subnets and VLANS using just a L2+ switch because it seems impossible to do this.

I turned to use traditional method.  I connected the VLANS to a router.

  @MatthewLi I have managed to achieve the same as you did but also cannot ping "past" the designated VLan port IP either. Although the demonstrations I have seen, show that pinging devices on alternate networks is possible. It did not work for you or me. It is a huge shame because these 3428X switches were recommended by our external provider but appear to fall short of doing the Inter-VLAN switching we needed. I have also found that you cannot subnet the VLAN IP. i.e 192.168.0.1/25 192.168.0.128/25

Anyone else have any other information to show I am perhaps missing something?

  @StephenL  TL-SG3428X is a L2+ switch.  It cannot do "IP forwarding" as a L3 switch.  So I gave up configuring the switch with VLANs and subnets.  It is impossible to forward packets between VLANs with different subnets like a L3 switch or a router.  I think TP-Link should state clearly the differences so that customers won't purchase a switch which cannot meet their needs.  In order to use subnets with VLANs, a core switch or a firewall(router) is needed.