eBay API Permissions Issue, using eBay API Explorer

Question

I have created a user token with a production environment application and a real production user. I'm using the API Explorer and have pasted the user token in the Token field, tried to make a basic createOrReplaceInventoryItem with their example, and I get this response:

"errors": [
{
  "errorId": 1100,
  "domain": "ACCESS",
  "category": "REQUEST",
  "message": "Access denied",
  "longMessage": "Insufficient permissions to fulfill the request."
}

When I created the application keys in eBay Developers, there were no options given for which APIs or calls I needed. Why would I not have sufficient privileges?

I tried using a few of their boilerplate samples: basic, advanced, a few different calls. The endpoint is: https://api.ebay.com/sell/inventory/v1/inventory_item/MY_SKU_HERE

The request body is their prefilled one:

"availability": { 
    "shipToLocationAvailability": { 
        "quantity": 50
    }
},
"condition": "NEW",
"product": { 
    "title": "GoPro Hero4 Helmet Cam",
    "description": "New GoPro Hero4 Helmet Cam. Unopened box.",
    "aspects": {
        "Brand":[
           "GoPro"
           ],
        "Type":[
           "Helmet/Action"
           ],
        "Storage Type":[
           "Removable"
           ],
        "Recording Definition":[
           "High Definition"
           ],
        "Media Format":[
           "Flash Drive (SSD)"
           ],
        "Optical Zoom":[
           "10x"
        ]
    },
    "imageUrls": [
        "http://i.ebayimg.com/images/i/182196556219-0-1/s-l1000.jpg",
        "http://i.ebayimg.com/images/i/182196556219-0-1/s-l1001.jpg",
        "http://i.ebayimg.com/images/i/182196556219-0-1/s-l1002.jpg"
    ]
}