Hi and welcome to the forum!!

You should probably check to see if there is anything in the cell itself - that's why they put the unions on it. Also try the diagnostic button - if you press it 5 times you will see a number with a "-" in front of it - that's what the unit is reading the salt as at that moment.

There is always the possibility of a bad cell - but I'd check the other 2 things first - there is also the possibility that the mother board got fried - have you had any lightning in the neighborhood lately?