createOrReplaceInventoryItem call failed with 'Insufficient permissions to fulfill the request' error

Question: I am getting ErrorCode 1100 as below with the createOrReplaceInventoryItem call endpoint: https://api.ebay.com/sell/inventory/v1/inventory_item/{SKU}
{
 "errors":[
   {
    "errorId":1100,
    "domain":"API_CATALOG",
    "category":"REQUEST",
    "message":"Insufficient permissions to fulfill the request."
   }
  ]

}
 

Answer: There might be several reasons for API failure. However; one of the reasons is that the createOrReplaceInventoryItem call of Inventory API does not allow Auth'n'Auth or Application token. The createOrReplaceInventoryItem call requires an access token an created with authorization code grant flow. User need to use OAuth access token an created with authorization-code-grant to execute the Inventory API calls.