Sandbox API access

I have created a Sandbox environment.

I have got the Postman Rest Api collection as per https://www.zoho.com/crm/developer/docs/api/v2/api-collection.html

I added a "Self Client" at https://api-console.zoho.com/ and then generated a Code (and selected CRM / Sandbox environment) entering "ZohoCRM.modules.ALL" as the Scope.

I ran "Generate Access Token and Refresh Token" in Postman which returned a "api_domain" of https://www.zohoapis.com. I checked that the access_token and refresh_token values were stored in the "Zoho environment" in Postman.

I then ran "Modules" in V2.1 which returned this:

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

What am I doing wrong?