During reassembly, follow these steps to reinstall the antenna:

Remove any leftover adhesive from the earpiece speaker and antenna.

Before sticking the antenna to the earpiece speaker, fasten the earpiece speaker to the frame and install the front camera and sensors. Connect all three press connectors.

Apply a small piece of thin, double-sided tape, such as Tesa tape, to the antenna.

Finally, connect the antenna press connector, then stick it onto the earpiece speaker.