Facebook isn’t down, but it did start an odd trending topic on Twitter Friday night as confused iPhone owners tried to figure out why the social network logged them out. I haven’t found an explanation for why this happened, but it appears that everyone accessing the app via an iOS app has to log back in, and many people who use SMS two-factor authentication were initially having trouble reconnecting.

Based on social media posts, many of the people with two-factor authentication enabled were eventually able to log back in, but the SMS codes were very slow to send, and some have had to upload pictures of their ID to regain access.

A Facebook spokesperson gave Engadget the following statement: “We’re aware that some people are currently having trouble accessing Facebook. We believe this was due to a configuration change and we’re working to get things back to normal as quickly as possible.”

Update: According to a Facebook spokesperson, “On January 22, a configuration change caused some people to be logged out of their Facebook accounts. We investigated the issue and fixed it for everyone earlier today. We’re sorry for the inconvenience.”