Transferring repo from bitbucket to github failing

Your old project requires credentials for read-only access
We will only temporarly store them for importing.

This basically means that we need to give the BitBucket login ID and password. When I entered BitBucket ID and password, importing went through fine and I could then see the imported repo on github.

Use your Bitbucket credentials.

Note: if you have enabled two-factor authentication on Bitbucket. Go to Bitbucket settings and create app password. Use that generated password when you are authentication on GitHub instead of your normal Bitbucket password.

It also work for private repositories.