!PLEASE HELP! : 1994 Explorere 4x4 and Low Engage Probleme

Hello Everybody
I have a problem with my 1994 "4 liter" Ford Explorer.
I was driving at reduced speed when my back rear right tire rolled over a
massive stone and ever since my "4 by 4 and low range" engage switches no
longer function. At the time of this incident the engages were not turned
on, and living in France, I have no technical assistance or support (Ford
and other) in this matter. No one seems able to help me in the repair of
with this misfortunate technical hassle. Could someone help me find the
solution please? Could it be an electrical problem? Mechanical or other?
Thanks in advance.