So, assuming you're connecting the printer using the NETwork connection, what IP address does the printer now have?

What IP did you think it should have?

Do you know how to lock the printer IP using the EWS in the printer?

Does your router have the ability to assign the same IP to the same device.... always?

Well this Is what I did to fix mine

I Open my  browser
I signed  in to my router as administrator
Mine is 192.168.1.1
I went to status in my router
Then to local network
Then to DHCP Clients Table
                      This is how I found what  printer  address the  was
                      Then I typed the printer ip address into my browser
                     Mine happened to be 192.168.1.105
                     Yours will probably be different
That got me to the 1720dn printer menu 
I clicked on            Configuration
I clicked on            Print Server Settings
I clicked on           TCP/IP
I clicked on           Set static IP address.
I changed IP address from                192.168.1.105    To    192.168.1.125
and        Submit
Now you can get to the printer menu at  192.168.1.125

Go to run
 
Printers & Faxes
 Right click on Dell laser printer 1720dn
Properties
Ports
Add  port
Double click on Dell Enhanced      TCP/IP 

I named the port                                My dell laser 1720 dn
Where it  said enter a single IP address or host name I entered the new address 192.168.1.125
the clicked   OK

Right click on Dell laser printer 1720dn
Properties
Ports
Choose your new port