Before the reset, remove the battery from the door push for about 10 minutes, press the push a couple times to remove the residual voltage and put back the battery to start the reset.

To reset it, press and hold the 'L' button on the front of the chime until the chime plays a melody.

After the reset please try to pair them again, unplug the chime from the socket and plug it back in, the chime will ring.
Press the 'L' button again to enter the learn mode, the chime will ring to confirm.

Then press the bell push within 30 seconds, the chime will ring again to confirm that the bell push has been paired to the chime.