self assigned ip address

> I added a device with a new IP address within the DHCP range. [...]

   Not a useful description of anything.  "added" to what?  Did you add
a new device to your network?  Did you configure something on your
(unspecified) router related to this "a device"?  What is your "a
device"?  What is your router?  What is this "a new IP address"?  What
is "the DHCP range"?  How did this "a device" get its "a new IP
address"?  DHCP?  Static, assigned by you?  What are all the IP
addresses involved here?

> [...] After rebooting the added device, it still retain the old ip
> address given when first added by the DHCP. [...]

   Why should it change?

> [...] Have repeatedly deleted new IP address and reassigned, saving
> changes, but still not changed. [...]

   I don't know what that means.  "deleted" what, exactly, from where,
exactly?  "reassigned" what, exactly, to what, exactly, how, exactly?
As usual, showing actual actions with their actual results (error
messages, LED indicators, ...) can be more helpful than vague
descriptions or interpretations.

> Any suggestions?

   Explain what you want, and why.  Then, explain what you did, and what
happened when you did it.  What you think it all means is much less
useful than a clear description of actual events and observations.