Block rear diff Rzr 900 2013″

Hello. Please forgive me for my errors. I’m from poland and my english is easy.
I buy Polaris rzr 900 xp ranger fron 2013 years from france. It was very fast transaction and now a have a mamy problems.
The most important problems is that i have a block rear diff/wheels ?
I have a switch

but i’t is not working. All the time i have block rear wheels. when i turn on 4WD everything working – the front diff working but a have all the time block back wheel.
The switch awd it’s not orginal. Please help me how a can dislock back wheels ?

from awd switch