Most of the time, sock placement issues cause yellow notifications but they can occasionally trigger a red notification.
Below are some photo examples of what to avoid.
Sock Too Loose
The sensor is too far away from the baby's skin. Make sure the sensor is right up against the skin. You shouldn't be able to see the red light.
The Socks Is Backwards
The sock is on backwards. Notice how the notch is by the big toe. Make sure the notch is just behind the pinky toe.
The Sock Has Shifted
The sock has shifted towhere the notch is above or below the pinky toe instead of behind and on the side. Make sure the notch is just behind the pinky toe (approx 1 cm).
The Sock Is Too Far Forward
The sock is positioned too close to the front of the foot. This puts the sensor too close to the toes where it's more difficult to get a good reading.
The Sock is Too Far Back
The sock is too far up the foot. The sweet spot is where the notch is just behind the pinky toe.
The Sensor Is Blocked
Make sure there is nothing between your baby's foot and the sensor (such as a sock), as this could hinder readings.
The sock is snug and the notch is just behind the pinky toe on the side of the foot.