SIP SERVER NOT FOUND ERROR NEC SV8100

Hi, Need Help
                           I bought these Used NEC phones DT700 32 BUTTON for my Office, we are Using NEC SV8100 PBX. All the old phones are working perfectly fine,
                           But the New Used Phones I bought is giving issues by saying SIP Server not Found. .

                           I have tried a couple of things but no luck so far.
                                 I have Hard reset the phone first to clear all the old settings.

                                 Enable the DHCP Mode,  Entered the SIP Server IP Address, and enter the SIP Extension to be used, but No luck,

                            The same error says SIP Server not found.

                          I have even created a new Ext. on Web Pro with new Port, but no progress.

                          Is there is any specific configuration needs to be done before adding DT700 to SV8100, If Yes, What should I do?
 
                           I bought 5 phones like this, and all of that 5 is not working.

                     Can anyone help, please?

Thanks
Harman ChhabraUser Support TechAsked:
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nociSoftware EngineerCommented:
Please check if you have a VOIP Vlan, and of if the phones are in the right VLAN.
(is the PBX reachable when plugging a Laptop with right ipaddress into the phone connection?.
Harman ChhabraUser Support TechAuthor Commented:
Hi Noci, Thanks for replying back, but I was just missing one step which I just found out is that I was not inserting right SIP port .

Thanks,
Harman

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