Composer for premium extension not working

I'm trying to use composer to load a premium extension for the first time following these instructions https://docs.metabox.io/integration/#using-composer. Note in the below I have removed my actual license key for obvious reasons.

My composer.json file works if I only try for free extensions but when I run composer install or update I get this error:
curl error 23 while downloading https://packages.metabox.io/packages.php?key=<my-key>: Failed writing received data to disk/application

This is my composer.json file:

{
    "repositories":[
        {
            "type": "composer",
            "url": "https://wpackagist.org"
        },
        {
            "type": "composer",
            "url": "https://packages.metabox.io/<my-key>"
        }
    ],
    "require": {
        "wpackagist-plugin/meta-box": "^5",
        "wpackagist-plugin/mb-settings-page": "dev-master"
    },
    "extra": {
        "installer-paths": {
            "vendor/meta-box/{$name}": [
                "vendor:wpackagist-plugin",
                "vendor:meta-box"
            ]
        }
    },
    "autoload": {
        "files": [
            "vendor/meta-box/meta-box/meta-box.php",
            "vendor/meta-box/mb-settings-page/mb-settings-page.php"
        ]
    },
    "config": {
      "allow-plugins": {
        "composer/installers": true
      }
    }

Anyone know what could cause this?