Composer plugin install

When I try to install the wp-smuh-pro by composer I get the message " [Composer\Downloader\TransportException]
Invalid credentials for 'https://premium.wpmudev.org/download/452620056_wp-smush-pro-2.5.3.zip', aborting."

I am using the api-key as listed on https://premium.wpmudev.org/manuals/using-wpmu-dev/composer/