The sensor assembly is connected to the watch body with two cables. One of the cables is extremely short and its connector will automatically disconnect when lifting the sensor assembly.

To reconnect the short press connector during reassembly, line up the sensor assembly to the frame and squeeze gently.

Carefully lift the top edge of the sensor assembly with your opening pick until you can get a good grip with your fingers.

Don't try to remove the sensor assembly all the way yet. It's still connected to the watch body.