Tammy's right on ST01 but STAUTHTRACE is a nicer view of the tracing tool. You can trace across all application servers from one screen (ST01 requires multiple sessions for each app server) and also get the results in ALV format to analyse and use
As a note, you'll probably hit S_RFC objects first. Once you get to Analysis Authorisation object S_RS_AUTH, switch to your RSECADMIN (thought it's probably failing on different object)