Cannot delete "Unknown Device" from Router Greyed Out

[Woobar]

Hello, i am trying to delete an Unknown Device from my router but the device is greyed out as seen in the screenshot.  I have blocked it and we cannot figure out what the device is so we assume it is not ours at the moment.  How can I get the "greyed out" Delete selection to restore so I can delete it? It worked for other unknown devices but for some reason this one will not allow it.

  

[FURRYe38]

What NG router model do you have? 

Happen to know what kind of phone this is? 

If you have Apple or Android, besure to disable any MAC Randomizer or Wifi Private IP address features on this phones or pads as this will cause a Unknown or Dev host hame to appear. 

[Woobar]

Hello and thank you for your reply.  It is a Nighthawk Pro Gaming Router Model is XR1000.  We do have all iPhones in the house and this device is always shown in the Online section of the Device Manager.  I have all devices named there so I know if they are mine, but this one never seems to go to the "offline" section.  Thought maybe that is why I couldn't delete it.  I assume that by checking the "Block" Box that is is not able to access my WiFi, but I like to keep an eye on things and would rather it be gone.

[Netduma-Liam]

I'd suggest disabling 'Private address' from the iPhone Wi-Fi settings for the NETGEAR network. That way it can better recognise that it's an iPhone and make it clearer in Device Manager. 

The fact that it's online is the reason that you can't delete it, but yes as you say having it blocked means it has no internet access.

[Woobar]

Thank you kindly, I will check it my phone and iPad and will check my family's phones when I see them later.  Have a great day!