Akko aks2000

HELP!! We have recently bought our first caravan and have used it locally on a few occasions,  I attach the caravan too the tow hitch making sure the indicator on the stabiliser shows green to show it has engaged on the tow ball and then push the stabiliser handle down, the problem I have is that when we get to our destination the stabiliser handle has popped up , am I doing anything wrong?

thanks in advance