If you have SSH access to splunk server where user is unable to login. You can create a user-seed.conf , however may require to delete $SPLUNK_HOME//etc/passwd file or there might be a case where passwd file is delete accidently. Then password to that particular user can be set using user-seed.conf, which inturn create the passwd file containing user and encrypted password. For more details on creating user-seed.conf, follow below link https://docs.splunk.com/Documentation/Splunk/8.0.2/Admin/User-seedconf.
... View more