after the latest update, my s9+ won't connect to wifi. it just blinks red on the clean button and the app can't find it.

Diagnosis

The blinking red light on the Clean button of the iRobot Roomba s9+ following a firmware update typically indicates a "Network Handshake Failure." During the update process, the robot's internal Wi-Fi module may have encountered a timeout or a corrupted packet, causing the onboard network credentials to become desynchronized from the router's current handshake protocol. This essentially leaves the robot in a "limbo" state where it believes it is connected to a network that no longer recognizes its security token. This is often compounded by the s9+ attempting to connect to a 5GHz band when it is strictly compatible with 2.4GHz. If your router uses "Smart Steering" (combining both bands under one SSID), the update may have triggered a reset that causes the robot to attempt a connection to the 5GHz band, which it cannot sustain, resulting in the persistent red error light and the "Robot Not Found" message in the iRobot Home App.

How to Fix It

To resolve this, you must force the robot to clear its cached network credentials and enter a fresh pairing mode. Follow these exact steps:

1. Power down the robot completely by pressing and holding the CLEAN button until the light ring disappears.
2. Perform a hard network reset: Press and hold the SPOT and DOCK buttons simultaneously for exactly 10 seconds. You will hear a descending tone, indicating the Wi-Fi module has been reset.
3. Open the iRobot Home App on your smartphone and ensure your phone is connected to a 2.4GHz Wi-Fi network. If your router has separate names for 2.4GHz and 5GHz, select the 2.4GHz option.
4. Select "Add a Device" in the app and choose the s9+ model.
5. When the robot enters pairing mode (the light ring will pulse white), the app will prompt you to connect your phone to the robot's internal broadcast signal (usually named "Roomba-XXXX").
6. Once connected to the robot's signal, enter your home Wi-Fi password. Wait for the light ring to turn solid white, confirming the handshake is complete.

If That Didn't Work

• Disable "Band Steering" or "Smart Connect" on your router settings. The s9+ frequently fails to connect when the router tries to force it onto a 5GHz frequency. Create a dedicated 2.4GHz Guest Network specifically for the Roomba to bypass this conflict.
• Perform a full factory reboot. Press and hold the CLEAN button for 20 seconds. The light ring will spin; continue holding until it stops. This clears the system cache and removes any corrupted update fragments that might be blocking the Wi-Fi module.
• Check for signal interference. If your Clean Base is placed near a microwave or a large metal filing cabinet, the signal may be dropped during the update finalization. Move the base 3-5 feet away from other electronic appliances and try the pairing process again.
• Update the iRobot Home App. Sometimes the robot is actually connected, but the app version is incompatible with the new firmware version installed on the s9+, causing a false "Not Found" error. Check the App Store or Google Play Store for a pending update.

Heads Up

• Always ensure the robot is docked and charging before starting a firmware update; a power dip during an update is the primary cause of Wi-Fi module corruption.
• Avoid using special characters (like !, @, #) in your Wi-Fi SSID or password, as the s9+ network card can occasionally struggle to parse these during the initial handshake.
• If you change your router or Wi-Fi password, you must perform the SPOT + DOCK reset mentioned above; the robot cannot "search" for a new network on its own.
• Keep the sensors on the bottom of the robot clean; while it seems unrelated, a "Cliff Sensor" error can sometimes override the Wi-Fi connectivity status, causing erratic light patterns on the Clean button.