Environment
Retain Unified Archiving 4.x
Situation
Migrated Retain database and indexes to a new server.
Able to successfully access and log into the Retain Admin Console.
However, when selecting the 'Server Configuration' link, after a timeout period, receive an error 503: Service Unavailable
All the other configuration links work properly.
Resolution
Noticed that the copy of files to /opt/beginfinite/retain/RetainServer/WEB-INF/solrweb/WEB-INF/cfg/ lost the file ownership on the new server.
Corrected the ownership and then stopped and started Tomcat and was able to successfully access the Server Configuration link on the admin console.