@SKane9 

If you want to prevent that device from connecting to the Deco, why do you delete it instead of keeping it blocked?

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The Deco displays the MAC address of the device.  From that address, you can usually identify the manufacturer of the device.  You do not need the Deco to do that, you can do that online.

  @yves_b I am keeping it blocked.  I just deleted it to see if it would come back and it did.  And those Mac finders are not working.  So was wondering if someone here might have another solution as how to look up what kind of device it might be.  But if I can't get a good solution here, the device is blocked and will remain that way.

  @SKane9 I agree, device identification could be handled better, even old software would give you basic MAC information on the devices you don't recognize right off using the address. 
 

Simply displaying "phone" or "network device", which can make the less knowledgeable customer's concerned. At the very least, show manufacture information from the MAC address to give a hint. 
 

The real issue lies with the fact they've tried making the devices mostly rely on mobile phones for interface. So a lot of the more basic old features of routers have been neglected in favor of a pretty interface. 

  @SKane9 

You could use a "lan scan" software, it will perhaps provide more details about that device.