"code": "500","description": "Account not exists", mail api

I have been through all the steps and have a functioning Oath access_token etc etc... I then

GET https://mail.zoho.com/api/organization And get my zoid

then

GET http://mail.zoho.com/api/organization/<hidden>/accounts and get the account details, which list the two accounts.

I then try and get a list of folders using the accountId's from the previous step, by hitting

GET https://mail.zoho.com/api/accounts/<accountId>/folders

The first of the two accountId's returns a list of folders, but when I use the other accountId I get back

{
    "status": {
        "code": 500,
        "description": "Account not exists"
    },
    "data": {}
}
The first accountId is that of the super_user account I used to create the access_token, 
the other account is just a user account. 

Ive used hundreds of API's over the years, this one has to be the most backward, poorly documented disaster ive ever experienced. 
Even the example url's in the documentation are wrong, 