Unfortunately, If you are forgotten the Apex Admin password on oracle server. We can be reset it again with new password,

Login into your SQL Server,  

#  sqlplus /nolog  

SQL> connect sys/password as sysdba   

Connected to:

Oracle Database 11g Express Edition Release - 64bit Production

Then run the below command (apxchpwd.sql) and enter a new password. Password will be changed.

SQL> @@/u01/app/oracle/product/11.2.0/xe/apex/apxchpwd.sql
Enter a value below for the password for the Application Express ADMIN user.

Enter a password for the ADMIN user              [] 

Session altered.

...changing password for ADMIN

PL/SQL procedure successfully completed.

Commit complete.

SQL> exit

Open the browser and give new password.

Now, change new password as your wish,