A DHCP server "leases" an IP Address to a client ... in this case your PC.
If your PC ethernet interface states that it cannot obtain a DHCP lease, it means that your Vonage Router did not provide it one when your PC requested one.
If it cannot find a lease, I cannot see why it would say successful.
You can see if you have obtained an IP address and route information by viewing your Ethernet interface info.
I you are running a Desktop environment ... then there may be an icon for it.
otherwise ... open a terminal window and type in:
this should display information ... hopefully you have an IP Addresss.
if you type in:
sudo route print
you should see a default gateway (destination 0.0.0.0).