New build house smell

[Chester]

Sweet baby Jesus

 

[Josh89]

You could have another waste pipe concealed behind kitchen unit. If there is space for a washing machine but you have never connected it up. Then there will be a waste pipe with a trap where the water would of evapourating preventing it from doing it's job of keeping sewage smells out. Most bew builds will have two spaces for dishwasher and washing machine. I know you mentioned that smell stopped when plug on kitchen sink but that could be a coincidence and plus kitchen sink trap looks fine and you hadn't covered overflow. If there is space where another appliance cab go then check to see if the wooden panel as a small hole cut out for drain and water inlet can go. You will be able to remove panel by undoing screws. Hope this helps