Can't connect to the API

Can't connect to the API

I'm very familiar with API integration / coding / etc. But I seem to be unable to get past the first step of connecting to the Zoho API.

I believe I've taken the necessary steps as per:

1) Create an application and generate code (using https://api-console.zoho.com)
I used "Self Client", scope = ZohoCRM.modules.ALL, time duration = 10 minutes

2) Get access_token
form-data: grant_type = authorization_code, client_id = xxx, client_secret = xxx, code = xxx
RESULT:
{
    "access_token": "xxxx",
    "refresh_token": "xxxx",
    "scope": "ZohoCRM.modules.ALL",
    "api_domain": "https://www.zohoapis.com",
    "token_type": "Bearer",
    "expires_in": 3600
}

3) Try to make an API request:
HEADER: Authorization = <access_token from previous step>

ERROR RECEIVED:
{
    "code": "OAUTH_SCOPE_MISMATCH",
    "details": {},
    "message": "invalid oauth scope to access this URL",
    "status": "error"
}

Any help would be greatly appreciated.