Authorization through meteor social networks falls off?

Question

Node.js

Good evening! Some of our clients are faced with the fact that nothing happens when they log in via social networks. More precisely, they are authorized in a pop-up window, there is a redirect to our callback and that's it. White screen.
We use standard libraries. There are no special settings. Log is clean.

Answer 1

Everything turned out to be simple - they forgot to add the www subdomain to the allowed ones in the application settings (FB, VK, etc.) =)
Thus, people who went to www could not log in through social networks. Made a redirect from www, now everything is ok.