Quick answer for advanced users
Check your router settings for AP isolation (also called client isolation, wireless isolation, or guest network isolation) and turn it OFF for your main network. Also make sure your phone and the smart devices are on the same subnet—same SSID, same VLAN.
Why this happens
I've seen this exact problem at least a dozen times. The app—say, Philips Hue, TP-Link Kasa, or Wyze—can't see new bulbs, plugs, or sensors. The user installs everything, follows all the steps in the app, but the device never shows up. Usually it's because the router is running two separate networks under one name, or it's blocking mDNS traffic which is how most smart home devices announce themselves.
Had a client last month with a Netgear Orbi system. He was sure it was the device firmware. Turned out the router had a hidden guest network that was identical to his main SSID, but it was isolated. All his phones connected to the guest network automatically, and the smart devices couldn't see them. Classic.
Step-by-step fix
- Find your router's IP. On Windows, open Command Prompt and type
ipconfig. Look for Default Gateway. On Mac, go to System Settings > Network > Wi-Fi > Details > Router. Usually it's something like 192.168.1.1 or 10.0.0.1. - Log into your router. Open a browser, type that IP, and enter your admin username and password. If you don't know it, check the sticker on the router or the manual. Defaults are often admin/admin or admin/password.
- Look for AP isolation. Head to the wireless settings section. The exact name varies: on TP-Link it's "Wireless Isolation" or "AP Isolation"; on Asus it's "Access Point Isolation"; on Netgear it's "Client Isolation". Disable it.
- Turn off guest network isolation. If you're using a guest network, go to its settings and disable "Access to Local Network" or "Allow guests to access my local network". This is often ON by default on newer routers for security.
- Check mDNS settings. Some routers (especially mesh systems) have an option to filter or block multicast traffic. Find it under Advanced > Network or LAN settings. Enable IGMP snooping if available—this helps multicast work properly.
- Restart everything. Reboot your router, then your phone, then the smart device. Wait two minutes between each. It clears the ARP cache and forces a fresh discovery.
Alternative fixes if the main one fails
If you still can't see devices, try these:
- Use the 2.4 GHz band only. Many smart devices (especially older ones) only work on 2.4 GHz. If your router has separate SSIDs for 2.4 and 5 GHz, connect your phone to the 2.4 GHz one. If it's a single SSID, temporarily disable the 5 GHz radio in the router settings, discover your devices, then re-enable it.
- Factory reset the smart device. I know it's annoying, but sometimes the device gets stuck in a bad state. For most smart plugs or bulbs, you hold the button for 10 seconds or power cycle it three times. Then try discovery again.
- Turn off the VPN on your phone. If you're running a VPN app (like NordVPN or ExpressVPN), it can interfere with local network discovery. Disable it temporarily.
- Try a different app. Some devices have their own discovery app (like the Philips Hue Bluetooth app). Use that first to confirm the device works. Then switch to the main app.
Prevention tip
Once you get it working, save your router's configuration as a backup file (most routers have this option under Administration or System). If you ever reset the router, you can restore it in seconds instead of troubleshooting all over again. And next time you buy a new router, check the manual for AP isolation settings before you start installing smart devices—it'll save you an hour of head-scratching.
One more thing: if you have a mesh Wi-Fi system (like Eero, Nest, or Orbi), check the app's settings for "Device isolation" or "Client isolation". These systems often hide these options under advanced network settings, but they're there. Turn them off for the main network, and keep them on for the guest network only.