magento2 – Error at Extension Manager

in Extension Manager i get this error:

Command "show" failed: Failed to clone the git@github.com:i-ways/magento2-paypal-plus.git repository, try running in interactive mode so that you can enter your GitHub credentials In Git.php line 354: Failed to execute git clone --mirror 'git@github.com:i-ways/magento2-paypal -plus.git'

What can I do?