Thank you for your response MattWho! I didn't just copy configuration files between versions. I did update core configuration files such as nifi.properties and manage it through Ansible. I just copied certificates (jks), flow.xml.gz (flow file) and authorizations.xml (to save my permissions, it is not related to the flow initialization I guess). Anyway I listen to your recommendations and setup it clearly with fully updated files without any of configuration files from previous versions but no luck. My Flow still cannot be initialized.   At least my previous version 1.11.4 won't start with that flow.xml.gz too unfortunately. Seems it some broken there, but I have no clue. One thing I could markup that I installed and used ProtobufProcessor. I have backup flow file behind two months ago and it's worked. I updated NiFi cluster to 1.23.0 and seems its all okay now. ... View more