==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version 1.6.6
- Deployed with iRedMail downloadable installer
- Ubuntu 20.04
- Store mail accounts in which backend: PGSQL
- Web server: Nginx
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I manage 2 iRedmail/Admin-Pro servers, upgrade with the same procedure to 1.6.6. Including upgrade to Roundcube 1.6.4.

I upgraded Roundcube by copying the files to /opt/www/roundcubemail-1.6.4, then copying skins/plugins and the config.inc.php file from the old version. Moved the symbolic link to the new directory. It now looks like this:
          roundcubemail -> roundcubemail-1.6.4/
          roundcubemail-1.5.2
          roundcubemail-1.6.4

On the one server Roundcube works as expected, login with username password and access to mailbox.

The other server shows the Roundcube login as attached screen shot. In addition to username password it asks for server. I tried: 127.0.0.1, it then seems to login but to an empty mailbox.

I ran a diff between the Roundcube config.inc.php of the both servers:

4c4,6
< $config['db_dsnw'] = 'pgsql://roundcube:secred_for_server_1@127.0.0.1:5432/roundcubemail';
---
> $config['db_dsnw'] = 'pgsql://roundcube:secred_for_server_2@127.0.0.1:5432/roundcubemail';
> $config['product_name'] = 'HeuvelTop Webmail';
> //$config['skin_logo'] = '...';
46c48
< $config['des_key'] = 'des_secred_for_server_1';
---
> $config['des_key'] = 'des_secred_for_server_2';
49c51
< //$config['username_domain'] = 'xxxx.nl';
---
> //$config['username_domain'] = 'yyyy.nl';

Searching for this issue I found one message related relating to a very old version of Roundcube.

What to do next?