New lawn is dying

Hello,
We previously had decking/flags down at the area of the garden where the lawn is, it was put down by a local landscaper this was done 18th May.
There’s are very large brown spots appearing, now I do have a dog, I have added the rocks to her own water source which I thought would stop her urine burning the lawn. The spots seems very large which makes me think it isn’t her? From looking on google I was wondering if the landscaper hasn’t removed all the concrete/put down enough soil? What do you all think?
Thank you

 

That definitely looks like a dog. I've not had that myself with my dogs, but mine are much smaller and in a much bigger garden. For friends with labradors, that's what their gardens tend to look like.