VLAN - Tagging Query

I have a netgear switch and the following configuration is working.

   VLAN ID  PORTS
        1   1 2 3 4 5 6 7 8 
        10  1 2 3 u2002 u2002 u2002 7 8 
        20  u2002 u2002 3 4 5 u2002 u2002 8

Each port is untagged in the Vlan. eg: VLAN 20 ports 3,4,5 & 8 are untagged.

The result of the above is anything coected to port 1, 2 & 7 can't see anything in port 3, 4 & 5.

Port 8 is a link to my router and port 3 a PC that sits across all VLANS.

This works as I want.

I have a device I'd like to add to coect to port 3, but using VLAN tagging on the device have it sit in VLAN 10 and get a DHCP address from VLAN 10.

On the device I've set VLAN 10 and on power up it just sits there waiting for DHCP..

Should this work ?

Thanks

UPDATE When the device is plugged into a LAN port on my router, I see no activity on the DHCP Server.

When it's coected to a port in VLAN10 I get activity on the DHCP server, but the device doesn't get a DHCP address.