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,
SQL> connect sys/password as sysdba
Oracle Database 11g Express Edition Release 22.214.171.124.0 - 64bit Production
Then run the below command (apxchpwd.sql) and enter a new password. Password will be changed.
Enter a value below for the password for the Application Express ADMIN user.
Enter a password for the ADMIN user 
...changing password for ADMIN
PL/SQL procedure successfully completed.
Open the browser and give new password.
Now, change new password as your wish,