To contact AdGem regarding an issue with an Offer hosted on their Offerwall, go to the earn page Here, scroll down to “Offer Partners.” Then open up their offerwall and click the three lines at the top left, from there click the "Reward Status" option and follow the instructions to contact them accordingly:
Additionally, you can get in touch with them for general inquiries via the link below: https://adgem.com/contact-us/