Why is 家里我们有一只猫 wrong?
I know, So frustrating
It's not the construction they're aiming for. I don't think it's wrong per se.
It is not wrong right now. I wrote it and it's accepted. July 2020
Should also accept 有只猫， 只猫 is like a cat, and 一只猫 would rather be like one cat
In this case the character 只 is the classifier for animals. In traditional Chinese it is a different character: 一隻貓
For Mandarin(and apparently Cantonese隻) 只(zhī) is a classifier for: one of a pair (hands 手, legs), birds 鸟, and some animals (cats 猫, etc.)
We have a cat at home is different from our home has a cat.
No 的mark, so 家里 is the plqce of the sentence, not the subject.
在家我们有一只猫． Is this not OK?
Mom, can we have a cat?