AirPort Utility 5.6.1 not discovering devices

On my windows 10 laptop, the AirPort Utility 5.6.1 doesn't send any packets when it's supposed to be scanning the network, so hitting rescan does literally nothing.

As other posts say, you should be able to connect to it by pulling down File, Configure Other, and providing the IP address (the default is 10.0.1.1) for the AirPort and your wifi password. If you changed the AirPort to use a different IP address but it's still acting as your router, look up your computer's default gateway and try that.

If you've reconfigured your network to use a different device as the router and can't remember the IP address you assigned to the AirPort, you can use a port scanning tool like nmap to scan your subnet for an open port 5009. Look for the response where the State is "open". Change the nmap command to reflect your own subnet.

nmap 192.168.1.0/24 -p 5009

Nmap scan report for 192.168.1.250

Host is up (-0.075s latency).

PORT STATE SERVICE

5009/tcp open airport-admin

MAC Address: 64:A5:C3:5F:FF:FF (Unknown)

Great input! nmap is also available for OS X & Linux systems as a method to discovery "missing" base stations, but could pose to be a bit difficult for those whom may not be familiar with networking fundamentals.

Of course, an alternative, is to just to temporarily connect to the base station by Ethernet.

Is there any reason Apple doesn't fix the bug in the AirPort Utility that keeps it from sending MDNS queries over wifi? Or is there just some subset of clients that it doesn't work for? My Windows 10 laptop doesn't have an Ethernet port to test that with. Running the utility on my Windows 2012 R2 server plugged into a switch that's plugged into my Buffalo router which my AirPort is also plugged into works fine, because the utility sends the MDNS query successfully and the AirPort replies, as it would work over wifi if the utility sent the query.

???

As you are already aware, mDNS is typically associated with Zero Configuration Networking (ZCN). Apple's implementation of ZCN is Bonjour, previously Rendezvous. The AirPort base stations utilize Bonjour for both service discovery and, for the Express, AirPlay.

I'm not aware of any restrictions of using any of these protocols over wireless vs. Ethernet. Being curious, I just ran a few Wireshark captures that show mDNS message activity to/from my base stations over both connection types.

When you say that your network looks like this......Internet Cable > Modem > Wi-Fi Booster Router > Airport Base Station.....I assume that the AirPort Express connects wirelessly to the network, correct?

We also assume the you have the current version of the AirPort Express, which has two Ethernet ports on the device.

Connect an Ethernet cable from your Mac to a LAN <--> Ethernet port on the AirPort Express

Temporarily turn off the WiFi on the Mac

Restart the Mac

Restart the AirPort Express

Start up AirPort Utility on the Mac to see if it will discover the AirPort Express

Please check again to see that I suggested that you temporarily connect an Ethernet cable from your Mac to the AirPort Express.....not from your WiFi router. The steps are listed above.

Report back if this method allows AirPort Utility to see the settings on the AirPort Express, so we can check some settings.

Please note that an A1084 version of the AirPort Express is at least 8+ years old, and as much as 11....and the average useful life of this product was about 3-4 years.....so that may come into play here.