Amadeus API - issue with the 'Flight Inspiration Search' API with 'origin' on LIVE mode

Question

I am attempting to ping: https://api.amadeus.com/v1/shopping/flight-destinations with origin 'MAN' on LIVE mode but receiving the following error:

{"errors":[{"status":500,"code":141,"title":"SYSTEM ERROR HAS OCCURRED","detail":"DATA DOMAIN NOT FOUND FOR REQUEST"}]}

I understand on TEST mode the origin airports are limited as per documentation on GutHub (https://github.com/amadeus4dev/data-collection/blob/master/data/flightsearch.md), but shouldn't this work on LIVE mode?

Here are the params I am passing:

$data = array(
    'origin' => 'MAN',
    'departureDate' => '2020-10-01,2020-10-31',
    'oneWay' => "false",
    'nonStop' => "false",
    'maxPrice' => "300",
    'viewBy' => 'COUNTRY'
);

When I change origin to 'LON' or 'LAX', it shows no errors and returns data. Do you know what is wrong? Many thanks in advance!