How to upgrade Magento Enterprise Edition?

I am a newbie for the Magento enterprise edition. I am upgrading Magento 2.3.5-p2 to Magento 2.4.0 in Enterprise Edition.

Following commands used with MySQL 5.7 and php7.3:

 composer require magento/product-enterprise-edition=2.4.0 --no-update
 composer update

During ‘composer update’ getting an error from the Magento module.

I have tried with included Magento keys in the auth.json file. But it’s not worked. Did I add keys from the purchased account will it work? or any other solution for this error.

The “http://xxrepo.xxx.com/dist/magento/module-ui/magento-module-ui-101.2.0.zip” file could not be downloaded (HTTP/1.1 404 Not Found)

Please let me know if anyone knows how to resolve this.

Thanks.