monitor saying low, advanced digital saying high

i became pregnant last 2 years ago using the old style fertility monitor.  i want to get pregnant again now, so I turned it on - it said to change the batteries, so i did - then it seemed ok.  THe first month it said i was at low fertility despite testing MANY days.  my period came as expected.  this month i decided to back up using the advanced digital sticks - at day 13 the sticks began to say high fertility (still saying it) while the monitor has continued to say low fertility.  I'm wondering if i can get a replacement for the monitor and a refund for the first month of sticks?