My link returns 404
The link (or that short URL) was deleted, or has expired.
Either the link - or that specific short URL - was deleted, or it's past its expiration date. Deletion is permanent, so if that's what happened, you'll need to create a new link rather than restore the old one.
If the link uses a custom domain, also check Branded link isn't resolving.
Related articles
Analytics are delayed - Expected lag, not lost data.
My analytics isn't updating - Give it a few minutes - dashboard views can lag slightly.
My analytics look wrong - Clicks not showing, delayed data, or numbers that don't match another tool.
Attribution isn't working - Usually means the link isn't attached to the video yet.