If you’re getting trouble with Prestashop Key, you can follow this step:

1. Login to the back-end of your store with Prestashop, select Advanced Parameters -> Webservice from toolbar.
   
2. Click Add New Button at the top right.
   
3. Type 32 random charachter in textbox, or you can click Button Generate!
   
4. Give check mark to all of resources or just this following resource: combinations, categories, image_types, images, products. Make sure that status is enable.
   
5. Click button save at the top right corner. Your key is ready too use.