thermostat keeps losing connection to wifi. i have to keep re-adding it in the app every few days.

Diagnosis

The Honeywell Home T10 Pro is experiencing a "DHCP lease expiration" or a "frequency steering" conflict. Because this device utilizes a low-power Wi-Fi chip designed for 2.4 GHz stability, it often struggles when connected to modern "Smart Connect" or "Mesh" routers that combine 2.4 GHz and 5 GHz bands under a single SSID. When the router attempts to "steer" the T10 Pro to the 5 GHz band—which the thermostat cannot maintain—the connection drops, and the device fails to automatically reconnect, requiring a manual re-provisioning in the Resideo app.

Furthermore, this issue is frequently caused by an IP address conflict. If your router is assigning dynamic IP addresses, the T10 Pro may be attempting to claim an address already occupied by another smart device (like a bulb or plug). This causes the thermostat to be kicked off the network every few days once the DHCP lease expires. You can confirm this by checking your router's client list; if the T10 Pro appears as "Offline" while other devices in the same room are connected, the issue is local to the thermostat's handshake with the gateway.

How to Fix It

To permanently stabilize the connection, you must isolate the 2.4 GHz band and assign a static identity to the device. Follow these exact steps:

1. Clear the Cache: On the T10 Pro physical interface, press Menu > Preferences > Wi-Fi > Forget Network. Then, open the Resideo app on your smartphone, go to the device settings, and select Remove Device to clear the cloud registration.
2. Separate Your Wi-Fi Bands: Access your router's admin panel (usually via 192.168.1.1 or 192.168.0.1). Disable "Smart Connect" or "Band Steering." Create two distinct SSIDs: one for 2.4 GHz (e.g., "Home_Wifi_2.4") and one for 5 GHz (e.g., "Home_Wifi_5").
3. Assign a Static IP: In the router's DHCP settings, find the MAC address of the T10 Pro (found under the Wi-Fi settings menu on the thermostat). Assign a "Reserved IP" or "Static IP" to this MAC address. This prevents the IP conflict that causes the disconnect every few days.
4. Re-Provision: Power cycle the thermostat by removing it from the wall plate for 30 seconds and snapping it back in. Open the Resideo app, select Add New Device, and connect the T10 Pro specifically to the new 2.4 GHz SSID.
5. Signal Verification: Ensure the thermostat shows at least three bars of signal strength. If it shows one or two bars, you may need a Wi-Fi extender placed halfway between the router and the thermostat.

If That Didn't Work

• Change the DNS Server: Some ISP-provided routers have unstable DNS settings that cause the T10 Pro to lose its handshake with the Resideo cloud servers. In your router settings, change the Primary DNS to 8.8.8.8 and the Secondary DNS to 8.8.4.4 (Google Public DNS). This often resolves the "connected to Wi-Fi but not to app" error.
• Adjust Channel Width: Set your 2.4 GHz Wi-Fi channel width to 20 MHz instead of "Auto" or "40 MHz." The T10 Pro's wireless radio is more stable on a narrower, more consistent channel, especially in crowded apartment environments where signal overlap is high.
• Verify C-Wire Voltage: If the thermostat is losing power momentarily, the Wi-Fi chip is the first thing to shut down. Use a multimeter to check the voltage between the R and C wires at the wall plate. It should be a steady 24VAC. If it drops below 22V, the Wi-Fi will intermittently drop, regardless of your router settings.
• Disable Firewall "MAC Filtering": Check if your router has an active MAC filter or "Access Control" list. If enabled, the router may be blocking the T10 Pro after a certain period of inactivity, treating it as an unauthorized device.

Heads Up

• Avoid 5GHz: Never attempt to force the T10 Pro onto a 5 GHz network; it will either fail to connect or drop every few hours.
• Avoid Metal Obstructions: If your thermostat is mounted on a wall with metal studs or directly behind a large appliance, the signal attenuation can cause the "ghost" disconnects you are experiencing.
• Firmware Updates: Always keep the Resideo app updated. Firmware pushes for the T10 Pro happen automatically over Wi-Fi, but they require a stable connection to complete without corrupting the network settings.
• Router Reboots: If you have an older router, schedule a weekly automatic reboot. This clears the ARP cache and prevents the IP conflicts that plague smart home devices.