How can you check the cause?

You have configured a Gateway SSO authentication using X.509 client certificates. The configuration of the dual trust relationship between client (browser) and SAP Web Dispatcher as well as the configuration of the SAP Web Dispatcher to accept and forward client certificates were done. Users complain that they can’t log in to the back-end system.

How can you check the cause?
A . Run back-end transaction SMICM and open the trace file
B . Run back-end system trace using ST12
C . Run gateway transaction /IWFND/TRACES
D . Run gateway transaction /IWFND/ ERROR
E . OG

Answer: D