Why cant my sim diagnose pets?

i was wondering if any of you know how to fix a little issue im having/know what could be causing it. My sim owns a vets (she has maxed out vet and training skills) but when she goes to examine an animal, it flags up that its scanning but the examination comes up saying diagnosis unknown.

Do i need to learn/read something so she can dignose, need a item. etc...?

I've tried googling it but nothing is coming up.

Any help would be appriciated.

Thank you.