Start won't start after upgrade - TLS configuration change
If upgrading from v8/v7 to v9 and HTTP/S is configured for web console security, you will need to adjust your Tomcat settings as described in these
upgrade troubleshooting steps. The reason being, MailArchiva V9 now embeds Tomcat 10 and its TLS connection configuration in server.xml has changed.
Server not archiving after upgrade - Legacy volume format change
If still using legacy V1 and V2 volume formats, it will be necessary to switch to V3 volume format since V1 and V2 volume formats are now marked as read-only. To switch the volume format, go to Configuration→General→Archive, select volume format to V3. Save. Visit Configuration→Volumes, create a new volume and close the existing Active one. Save.