If you wish to show Paylater on Payment links, you are required to add "items" parameter during payment links creation as it is mandatory from our partner. 

If you create via Dashboard : 

If you create via API : 

 "items": [
            {
              "name": "Air Conditioner",
              "quantity": 1,
              "price": 100000,
              "category": "Electronic",
              "url": "https://yourcompany.com/example_item"
            }
          ]