After Oracle Database Upgrade to 12.2, Database Express Did not work

I upgraded one database from 11.2.0.4 to 12.2.0.1 on one Solaris Sparc server. After that I configured the Enterprise Manager Database Express, but when I tried to access it, I got the following error:

For more information about Oracle Enterprise Manager Database Express, please refer to my post:
https://ahmedfattah.com/2018/10/14/oracle-enterprise-manager-database-express-12c-overview/

Environment:

• Oracle Solaris 11
• Oracle Restart 12.2.0.1
• Oracle Database 12.2.0.1
• Role separation implemented (grid user for GI an oracle user for database)

 Database Express Setup:

Following are the main configuration steps:

So, all the necessary normal setup tasks were done successfully. Also, I confirmed that there is no firewall or proxy between the database server and the client accessing the database express.
Client can ping the database server either by hostname or by IP.But,I’m still getting the error:

So, what is the issue?

After some research, I found the main issue, which is the wallet files permissions.
The wallet files should normally have permission 0600, but that doesn’t allow successful display of the EM Express page when RDBMS sits on top of GI with role separation.

The XDB wallet is stored in the $ORACLE_BASE/admin/<db_name>/xdb_wallet directory . If ORACLE_BASE is not defined, the XDB wallet is stored in $ORACLE_HOME/admin/<db_name>/xdb_wallet, where <db_name> is the unique database name.

Changing mode to 640 to allow for group oinstall to read the wallet files makes the EM Express page available via browser.

This fixed the issue, and I can successfully access the EM Database Express:

References:

Troubleshooting Why EM Express is not Working (Doc ID 1604062.1)
https://community.oracle.com/thread/3995345

Thanks
Ahmed