I have got two fresh installations of Portal on seperate machines. Both have same versions and are authenticated. I have created portal on one of them. For second one when I try to join the existing portal I am getting error of 'unable to generate token from primary machine' (screen shot below). Can anyone has any idea on why the issue is happening. The username and password are correct.
You may be using an incorrect URL for the Portal URL. Take the URL entered, append /arcgis/sharing/rest, (https://portal.domain.com:7443/arcgis/sharing/rest), and see if it redirects anywhere. If it does, use the new URL as the Portal URL.