Does anyone know why a workflow might not work when scheduled? When I put the WF in testing mode, and click execute now, it works, so I'm confused why it doesn't when scheduled. Sometimes it will and sometimes it won't

And you definitely checked that saved search filter you have set there? I.e. that the record is one of the search results, specifically at the time the workflow is scheduled to run.

@James Morris yes! The saved search shows results where start date = today and then the saved search is set to run at 12:30am every day so it runs those results.

An you're not running this in a release preview account, right? B/c scheduled workflows don't run in RP, per Answer ID 103898. If it's not that and you're absolutely sure all your conditions are setup right to allow the workflow to trigger, then it's probably time to reach out to NS support and see what they say.

@James Morris yes this is in a production account. I was thinking about reaching out to support because of the irregular behavior

Make sure the audience of the workflow is set up how you want it. You might also consider running that workflow as an admin (there's a checkbox on the workflow record for this). That might make a difference too.