As an update, our team is aware of the issue affecting the process of linking freelancers' Facebook accounts to their Upwork account. Fixing the core issue is on our team's roadmap but we don't have an ETA at the moment. We apologize for the inconvenience and will follow up with more information once we receive a confirmation from our team.
I'm also having this issue. After clicking either Facebook/Google+, a window will open. It will then ask me to sign in but after signing in it will suddenly close the window. I tried connecting again many times using Facebook but Upwork will open a window then close automatically. My facebook account is still not linked after that. Thank you for the update about the issue. I was worried that I may be the only one experiencing it.
I am also having trouble linking my facebook account. The same problem. it opens a facebook login window, I login and then the window closes and upwork doesn't update. Please help!