We've resolved the issue and segments will continue to update as normal. Segments who had a 0 count will automatically refresh within a few hours. Some campaign delivery may have been impacted for sites targeting a segment with 0 subscribers during this window. This impacted only a handful of users and we will be reaching out to you directly if impacted to assist.
May 25, 16:24 UTC
A fix has been implemented and we are monitoring the results.
May 25, 16:10 UTC
We're investigating an issue where some segments that were updated on 05/24/19 between 1pm-4pm EST resulted in a count of 0.
May 25, 14:39 UTC