@Dahlgren  - Make sure you are using a Java 21 JDK and not a Java 21 JRE. - Try excluding the NiFi directory to include all the repositories from your Virus scanning software and see if that helps resolve the startup issue. Here is an Apache NiFi slack thread discussing this same issue: https://apachenifi.slack.com/archives/C0L9UPWJZ/p1731963549046199 Please help our community thrive. If you found any of the suggestions/solutions provided helped you with solving your issue or answering your question, please take a moment to login and click "Accept as Solution" on one or more of them that helped. Thank you, Matt ... View more