Just spotted this on brentozar.com via Twitter. The CU2 update for SQL Server 2019 plays havoc with SQL Agent on some systems causing jobs to not run among other things. Official workaround for now is to uninstall the CU.
See the below from Brent Ozar's blog for details and other links.
https://www.brentozar.com/archive/2020/03/breaking-news-sql-server-2019-cu2-breaks-agent/