Please first make sure that Over-ear detection is enabled in the Nothing X App.
Over-ear detection automatically detects whether the headphones are being worn and pauses or resumes playback accordingly. As the sensor is located inside the right earcup, removing or adjusting the right earcup may trigger a pause, while removing only the left earcup may not.
Wearing position and earcup fit may also affect detection. Please adjust the headphones to ensure the earcups fit securely over your ears.