Is he first born ? They may not realize the child is not developing and meeting age appropriate milestones ? I had first time parents with a 2 yr old non verbal child and they kept explaining away when I would mention dck development . Dck was a lot more one on one than I could give and eventually I gave notice . It was awkward as dcp were in so much denial that I'm sure they just thought I was over reacting when I would mention behaviour I wasn't comfortable with ie face smashing , head banging .
Do you have a trial time set up in your contract ?