Please know that this is a known issue, and our engineers are currently trying to resolve it. In the meantime, the Customer Support Team will reach out to you with more information about the issue.
I'm also having this issue: a window will open, ask me sign in, then close. After that, if I try to connect again, Upwork will open a window then close automatically. My facebook account is still not linked.
I cannot link my facebook or google accounts. It opens the windows ask me to sign in then close. It has done this multiple times and yet each refresh, or log out still shows no linked accounts.