Not always fluid related.
I got that terrible "Jacks Down" warning one time while driving on the highway in pouring rain. I stopped and checked the position of the jacks and they were all properly retracted. I disabled the alarm and returned home.
My investigation found the Trombetta switch for reversing polarity had a cracked housing. Water entered the housing and shorted out the solenoids tricking the system into thinking the jacks were deployed.
I ordered a new switch for under $60.00, installed it myself and things once more work as designed.
Moral of the story, check the fluid first but if that doesn't solve the problem you may have to dig deeper.