The problems weren’t limited to external users. Facebook’s internal communication platform, Workplace, went down altogether for most of the work day, said a person familiar with the matter who spoke on the condition of anonymity because they weren’t authorized to speak publicly. And as employees turned to third-party tools such as Slack, many found themselves locked out of even those, because Facebook’s mechanism for signing on to them was not working, said another person familiar with the matter who spoke under the same conditions.
