What's wrong with my provided admin password for Oracle Apex instance administrator account?

I have installed Oracle Database 19c Enterprise Edition on Oracle Linux 7.8.I am now trying to install Apex 20.1 . Got to the chapter "5.4.2.3 Running apxchpwd.sql" to set the instance administrator password. Executed the @apxchpwd.sql command, it asks me for user name, e-mail and password but then it gives an error as if the password does not have enough complexity, although the password I provide is literally H29dN8%Ih^^IV$Y3$j4Mx. Tried various other passwords, nothing seems to be acceptable. What can be the problem? Here is how I got to the error:

[oracle@oraclemachine apex]$ sqlplus /nolog

SQL*Plus: Release 19.0.0.0.0 - Production on Tue Aug 25 09:50:03 2020
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.

SQL> connect sys as sysdba
Enter password:
Connected.
SQL>
SQL> @apxchpwd.sql
...set_appun.sql
================================================================================
This script can be used to change the password of an Application Express
instance administrator. If the user does not yet exist, a user record will be
created.
================================================================================
Enter the administrator's username [ADMIN] apexadmin
User "apexadmin" does not yet exist and will be created.
Enter apexadmin's email [apexadmin] a@b.c
Enter apexadmin's password []
--------------------------------------------------------------------------------
PASSWORD_COMPLEXITY_ERROR
* PASSWORD_ONE_ALPHA_ERR
* PASSWORD_ONE_PUNCTUATION_ERR
* PASSWORD_ONE_UPPER_ERR
* PASSWORD_ONE_LOWER_ERR
--------------------------------------------------------------------------------
declare
*
ERROR at line 1:
ORA-20001: Password validation failed.
ORA-06512: at line 30
ORA-06512: at "APEX_200100.WWV_FLOW_FND_USER_INT", line 3744
ORA-06512: at line 20