NEW YORK — 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 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.

“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.”

The disruption seemed spotty, with some apps and parts of the apps working for some but not others. While some less active users may not have noticed that Facebook services were down, other frequent users and advertisers keenly felt its absence.