Ovulation tests! Ahhh

Ok so got a kit few months ago and it's all been fine and working. I get my new one so tried it this morning. Yesterday old test said high fertility this morning new test said nowt nothing zip! Omg ahhh so then after a mass panic I tried my old test and yep high fert again. This puts me in much doubt are they working fine?  Is one faulty if so which one. So many questions an no one to get answers from. All I can do is continue to do what I am doing. Maybe write to who I ordered it from. Ya never know might get a free one.  Anyway must dash to work xxx