Well, 5 years after opening this issue, with no responses here, I finally got into the source code and fixed it.

The problem seems to be if eLog is configured to prohibit users (non-administrators) from the "Config" option...but on the initial self-registration, the code goes to the Config screen for the user anyway...resulting in the false error message.

So, I [badly] hacked eLog to fix that, add some debugging/log messages, and to correct a typo.

Attached is the patch against release 3.1.1-1. Try not to cringe too much at my code. :)

*** ./elogd.c	Tue Aug 23 21:27:39 2016
--- ../../elog-3.1.1.orig/src/elogd.c	Tue Aug  4 09:30:54 2015
***************
*** 80,84 ****
  int _verbose_level, _current_message_id;
  int _logging_level, _ssl_flag;
- BOOL just_registered = FALSE;	/* flag to supress erroneous error */
  
  LOGBOOK *lb_list = NULL;
--- 80,83 ----
***************
*** 13363,13369 ****
  
     if (new_user) {
-       write_logfile(lbs,"In save_user_config() with new_user==TRUE, setting just_registered=TRUE");
-       just_registered = TRUE;
- 
        node = mxml_find_node(lbs->pwd_xml_tree, "/list");
        if (!node) {
--- 13362,13365 ----
***************
*** 13432,13436 ****
        mxml_write_tree(file_name, lbs->pwd_xml_tree);
  
- 
     /* if requested, send notification email to user or admin user */
     if (new_user && !first_user && (self_register == 2 || self_register == 3 || self_register == 4)
--- 13428,13431 ----
***************
*** 13616,13619 ****
--- 13611,13615 ----
                    };
                 }
+ 
                 pl = strtok(NULL, " ,");
              }
***************
*** 26649,26666 ****
     /* save user info if "save" is pressed */
     if (strieq(command, loc("Save")) && isparam("new_user_name") && !isparam("config")) {
!       if (!save_user_config(lbs, getparam("new_user_name"), TRUE)) {
           return 0;
!       }
!       if ( just_registered ) {
!          write_logfile(lbs,"In do_self_register with just_registered==TRUE, resetting flag, calling show_login_page(NULL,\"\",0)");
!          just_registered = FALSE;
!          show_login_page(NULL, "", 0);
!       } else {
!          if (lbs)
!             sprintf(str, "../%s/", lbs->name_enc);
!          else
!             sprintf(str, ".");
!          redirect(lbs, str);
!       }
        return 0;
     }
--- 26645,26655 ----
     /* save user info if "save" is pressed */
     if (strieq(command, loc("Save")) && isparam("new_user_name") && !isparam("config")) {
!       if (!save_user_config(lbs, getparam("new_user_name"), TRUE))
           return 0;
!       if (lbs)
!          sprintf(str, "../%s/", lbs->name_enc);
!       else
!          sprintf(str, ".");
!       redirect(lbs, str);
        return 0;
     }
***************
*** 27355,27364 ****
        /* check if user has access to logbook */
        if (!check_login_user(lbs, getparam("uname"))) {
!       	sprintf(str, "check_login_user access failure: user \"%s\", logbook \"%s\"", uname, lbs->name);
!       	write_logfile(lbs, str);
!          show_error("User has no access to this logbook.");
!          strlcpy(str, loc("New user"), sizeof(str));
!          url_encode(str, sizeof(str));
!          rsprintf("


<b><center><a href=\"?cmd=%s\">%s</a></center></b></td></tr>", str, loc("Register as new user"));
           return;
        }
--- 27344,27348 ----
        /* check if user has access to logbook */
        if (!check_login_user(lbs, getparam("uname"))) {
!          show_error("Use has no access to this logbook");
           return;
        }
***************
*** 27728,27747 ****
        strencode2(str2, command, sizeof(str2));
        strencode2(str3, full_name, sizeof(str3));
! 
!       if (strieq(str2,"Config") && just_registered  == TRUE ) {
! 	/* this is the only time to skip the error that "Config" is not an allowed command...as the Config was really
!            called in order to complete the self-registration
! 	  
! 	   now, reset the flag */
!        write_logfile(lbs,"In interprete() with just_registered==TRUE, resetting flag, skipping error message that user is not allowed to run command \"Config\"");
!        just_registered = FALSE;
!       } else {
!       	sprintf(str, "Error: Command \"%s\" is not allowed for uname \"%s\", full name \"%s\"", str2, uname,str3);
!       	write_logfile(lbs, str);
! 	
!       	sprintf(str, loc("Error: Command \"<b>%s</b>\" is not allowed for login \"<b>%s</b>\", user \"<b>%s</b>\""), str2,uname,str3);
!       	show_error(str);
!         return;
!       }
     }
  
--- 27712,27718 ----
        strencode2(str2, command, sizeof(str2));
        strencode2(str3, full_name, sizeof(str3));
!       sprintf(str, loc("Error: Command \"<b>%s</b>\" is not allowed for user \"<b>%s</b>\""), str2, str3);
!       show_error(str);
!       return;
     }