The elog client binary does not work with webserver authentication.  One fix would be to support both webserver and kerberos authentication (authentication = webserver, kerberos), similar to how you currently support 
"authentication = kerberos, file".

A more general discussion of the elog client binary with webserver authentication can be found at https://midas.psi.ch/elogs/Forum/68318 .

Many thanks,
Devin