The repo.magento.com repository is where Magento 2 and third-party Composer packages are stored and requires authentication. Use your Magento Marketplace account to generate a pair of 32-character authentication keys to access the repository.
You must ensure you are sharing access from the primary account, and pulling access keys from the same account. For more details please see this devdoc:
To generate a Shared Access point: https://marketplacesupport.magento.com/hc/en-us/articles/4411309254541