Unable to install Magento2 B2B module extension

I am installing magento2 B2B extension after creating auth.json and giving proper username and password i am getting following error.

composer require magento/extension-b2b 

 [ComposerDownloaderTransportException]
  Invalid credentials for 'https://repo.magento.com/packages.json', aborting.

and my auth.json file contain following code.

{
"http-basic": {
    "repo.magento.com": {
       "username": "muha********",
        "password": "Zx*********"
    }
}

}

anyone can help if possible