Updated at 7:10 p.m. on Thursday, March 14, 2019, with more information.
Facebook went down for almost a full day across parts of North America and Europe, but it's still not saying exactly what happened.
All the social network said Thursday was that the outages, which affected users and advertisers worldwide, resulted from a "server configuration change." It offered no further details.
Facebook and its apps — Instagram, Facebook Messenger and WhatsApp — started experiencing problems midday Wednesday on the U.S. East Coast. Facebook was still having sporadic issues Thursday morning.
Facebook did not say how many users were affected or why the outage took so long to fix. In a tweet about 24 hours after the problems began, Facebook apologized and thanked people for their patience. It didn't elaborate on the server change.
The outage is yet another publicity problem for a company already dealing with privacy issues and regulatory probes.
The disruption isn't likely to hurt advertisers much, since they usually pay for ads per click or impression. But they lose potential customers who might have seen their ads when the site and apps were down. Longer term, Facebook's reputation with advertisers and investors could be damaged, said Wedbush Securities managing director Dan Ives.
It didn't help that it took Facebook so long to explain what was going on, he said. Facebook said on Wednesday that the problem was not related to a "distributed denial of service" or DDoS attack, a type of attack that hackers use to interrupt service to a site, but didn't provide any other details until Thursday.
"In these situations a lack of transparency is not a good look," Ives said. "The longer something like this lasts, the more questions there are."