A scheduled video normally goes out within a few minutes of its slot. If one didn't:
Check the channel. If it needs reconnecting, nothing can upload. Settings, then Channels.
Check for a review hold. On manual approval Series, posts wait in review until you approve.
Check credits. If the render never started for lack of credits, the post is on hold. Top up within a day of the slot and it retries on its own; after that the slot is skipped and the next one proceeds normally.
Give it a few minutes. A publish that hit a temporary YouTube error retries on its own.
Still nothing? Message us in the chat with the Series name and the slot time and we'll look right away.