Receiving error on API Call: /api/2.0/auth/refreshToken

Getting a 400 error on requesting for access token from /refreshToken Endpoint:

Sample call: POST

curl -X POST \

    https://[COMMUNITY-DOMIAN]/api/2.0/auth/refreshToken \

    -H "Content-Type: application/json" \

    -H "client-id:[CLIENT-ID]" \

    -d '{

            "client_id":"CbEwdj3DjslDJLsldk30823480lkaXvNLvA=",

            "client_secret":"BV32987skdjfhSDlkajdhfASDF409234ItWs=",

            "grant_type":"refresh_token",

         "refresh_token":"ZVQaoDdkcsC/9vKZUw0OHEvKG3nd/HoIdwdHLNFwB8E=",

        }'

Error received:

Error code: 411

refresh_token + client_id+client_secret is NOT valid or refresh_token might have expired

We are using the correct parameters. Also, receiving the same error even after using 'force_refresh' in the call.