I found this a another site, hope it will be helpful..
HERE’S THE FULL RESET PROCEDURE PER LACROSSE TECH SUPPORT:
LaCrosse WS-2810 Full Startup/Reset Procedure
1. If the battery in the wind sensor has not charged in full sun (facing due south) for at least three days, do this first.
2. For this procedure, chances of success are better when the distances between the display unit and other sensors relative to the temp/humidity sensor are within 50 feet. Line-of-sight orientation and fewest possible intervening obstructions are desirable. Further separation can be done after start-up.
3. After solar battery is charged, go to the display unit and follow the following steps as, and in the order, listed.
4. Press and hold the Set button. Release when the display ‘blanks out’.
5. Repeatedly press and release Set button until the “rES off” message appears at bottom of screen.
6. While in the “rES Off” mode, press and release the Up Arrow to change the message to “rES On”. Then press the Set button (once).
7. A counter at the bottom of the page will now appear showing the value “127” and then it will begin counting down to “0”. When zero is reached, the display will show “rES dOnE”.
8. At this point, remove the batteries from the display.
9. While batteries are still out, press any key on the display at least 20 times. (This helps to drain any residual charges in the circuits)
10. Now remove the batteries from the rain sensor and the temp/humidity sensor.
11. Leave everything as-is for at least 10 minutes.
12. Now go to the wind sensor and press and release the reset button recessed in the little hole on the bottom of the wind sensor. Use the provided plastic ‘rod’ or a straightened paper clip. The switch is approximately 5/8” straight inside the case. The actuation requires very little pressure. If you do it carefully you can feel (but probably not hear) a soft switch movement.
13. Now replace the batteries in the rain sensor and temp/humidity sensor, followed by replacement of batteries in the display unit.
14. Leave everything as-is and display untouched for at least 10 minutes.
15. Everything should now be linked and the display should show connectivity and activity of all the sensors.
16. If something is still not functioning, you should call LaCrosse technical support.