To contact Monlix regarding an issue with an Offer hosted on their Offerwall, go to the Freecash Earn page here, scroll down to “Offer Partners” and open up their Offerwall. You can also open their Offerwall by clicking here.
Click on the 3 lines at the top right of the page and select the "Contact" option.
Then fill out the Contact Form.
Alternatively you can contact them directly via this link: https://monlix.com/contact