Authentication denied: Boot identity not valid

goto $domaindir/config/ and check config.xml to the 


security-configuration/realm/sec:authentication-provider 
    xsi:type='wls:default-authenticatorType"
    xsi:type='wls:sql-authenticatorType"



security-configuration/realm/sec:authentication-provide/sec:control-flag

if the authentication-provider is default-authenticatorType then follow the following steps:
1: remove the boot.properties file completely from the managed server directory.
2: remove the ManagedServerDir/data/ldap directory completely.


if it is SQL then need to make sure if you have correctly set the database config to connect:


xpath to check: security-configuration/realm/sec:rdbms-security-store>
   to config username, password-encrypted (db password), connection-url, driver-name, connection-properties