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Wajahat Ali 's answer worked for me. Thanks,

Sergio

Before you can use Glip API in sandbox, you need to login https://glip-app.devtest.ringcentral.com/ at least once manually using your sandbox account.

Please note that, do not sign up a new user. Use your existing user to login. It is the same user that you used to do RingCentral API authorization.

Please try and let RC Dev Support know if it won't work.
Thanks,

Even on any of glip API... Does any body find any solution??

<?php
// https://developers.ringcentral.com/my-account.html#/applications
// Find your credentials at the above url, set them as environment variables, or enter them below

// OPTIONAL QUERY PARAMETERS
$queryParams = array(
    //'recordCount' => 30,
    //'pageToken' => '<ENTER VALUE>'
);

require('vendor/autoload.php');
$rcsdk = new RingCentral\SDK\SDK(getenv('clientId'), getenv('clientSecret'), getenv('serverURL'));
$platform = $rcsdk->platform();
$platform->login(getenv('username'), getenv('extension'), getenv('password'));
$r = $platform->get("/restapi/v1.0/glip/conversations", $queryParams);
// PROCESS RESPONSE
?>

Anybody found any solution??

Looks like this needs to be checked with the RingCentral dev team in order to take it further. Also, ensure to capture the steps on where you are getting this error so that the team can investigate and get back to you

Please contact the developer support team through a help ticket with details and screenshots. They can help in this case.

You can also create a case in support portal registering the issue.