Could you please share more details of where you're experiencing the error you're referring to? I would also suggest trying and clear your cache and cookies or log in via another browser. Thank you.
I got the same message just now, every time I tried to connect my social link. I clicked link to Twitter and tried to login to Twitter then this error happened. I cleared cache, reloged to Upwork, tried to link my social account again, then the error kept on happening. Tried two attempts.
Same as when I tried to link to GitHub. Browser is Chrome.