Try a follow up with them. I got my first job simply because I was the only candidate that followed up and that showed initiative (according to the hiring manager) which made me stood out from the other candidates as profile wise, it was pretty neck to neck.

If it's already a week overdue, just follow up with them. Any method is fine, there is no hard and fast rule here. I'm usually a bit 'lansi' and just politely thank them for the opportunity and mention that I understand they are busy but would appreciate a response if or if not I am selected as I need to give an answer to other potential employer as well.