Authenticate issue for API usage

Hi,

so I'd like to access Zoho Books with REST API/python and tried following tutorial on https://www.zoho.com/books/api/v3/#oauth

Initially I created Self Client on https://api-console.zoho.com/ with Client ID and Client Secret.

Then I generated Code with Scrope ZohoBooks.fullaccess.all (while testing I also tried ZohoBooks.invoices.READ) and using it I tried the first step generating Oauth token with

https://accounts.zoho.com/oauth/v2/token?code=GeneratedCode&client_id=ClientID&client_secret=ClientSecret&redirect_uri=http://www.zoho.com/books&grant_type=authorization_code

However I always receive "An error occurred.

An error occurred while processing your request.

Please try again later."

I've also tried running in browser, console and Postman the first step on https://www.zoho.com/books/api/v3/#oauth

curl https://books.zoho.com/api/v3/organizations?organization_id=OrgID -H 'Authorization: Zoho-oauthtoken GeneratedCode'

I get (although I double check Organisation Id and its a 9 digit number)

{"code":15,"message":"Please ensure that the organization_id has less than 100 characters."}

while in Postman I get Status 200 OK but when I try to preview page - it doesn't show anything.

How should I approach this issue?