NEW YORK — Facebook says its lengthy outages over the past day were the result of a “server configuration change.”The outages affected countless users and advertisers worldwide. Some people weren’t able to reach Facebook’s website and apps, including Facebook, Messenger, Instagram and WhatsApp.The length of the outage is another publicity problem for a company already dealing with privacy issues and regulatory probes. The outages started midday EDT Wednesday. There were still sporadic problems Thursday morning.Facebook did not say how many users were affected or why the outage was so long. 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.