How to Reset Apex Admin Password on Oracle Server
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 18.104.22.168.0 - 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,