Ensure your PC is connected to the same network as your AirPort device.
AirPort Utility 5.6.1 does not support the latest 802.11ac models (the tall "tower" versions). For those, you must use an iOS device or a Mac. Troubleshooting Common Issues Download AirPort Utility 5.6.1 for Windows - Apple Support apple airport utility windows 10 download
If you have extremely legacy hardware, AirPort Utility 5.4.2 is also available. Installation & Compatibility Steps Ensure your PC is connected to the same