Please try to follow these steps carefully. (Even you already have this key, We still suggest you to create a new one because sometimes Envato api has the problem with caching.)
1. Login to Envato with the account that purchased this theme and go to this url : https://build.envato.com/my-apps/
2. At the bottom, click 'Create a new token'
3. Check on these settings: https://drive.google.com/file/d/14p-I2JljAjSwGsWo_LUU_nezw-eG1sru/view
- View and search Envato sites
- Download the user's purchased items
- List purchases the user has made
4. Copy the code here and save it somewhere safe: https://drive.google.com/open?id=1hK0Ygzlb75yw2mIFe4NnHSVyVvTFkSTX and click on the confirm button.
5. Back to 'Envato Market' menu in your backend and put the code https://drive.google.com/open?id=1E9Nk8_06C5u3HsZHmTRCCsl1U3wt-1CE and click on 'save changes'