Looking for a Google Tag Manager expert

i have issues with tracking my ecommerce conversions. The company who have build my website tells me that they installed the tags following google guidelines, but i dont get the data. So i'm looking for somebody who can tell me what's going wrong and how we have to fix this.

NOTE: i'm not looking for somebody who wants te solve the problem. I do not have acces to the code. I need proof that my developer has done something wrong and i also want to be able to show them what they have to do to make it work