Roundcube issues after server upgrade (Debian 10, PHP7)

Question

I have upgraded my DigitalOcean droplet from Debian 8 to Debian 10, as well as upgraded PHP from PHP5 to PHP7.3. I also upgrade RoundCube to 1.4.2.

Everything seems to work fine. I see no obvious log entries to this issue but I will try to outline it:

1. I am able to log into Roundcube with no issue.
2. I can see email files in /homes/vmail/domain.tld/username/new/
3. No emails are in the Inbox at all.
4. After sometime (seconds to minutes, cannot pin point at this point), the files under /homes/vmail/domain.tld/username/new/ are moved to /homes/vmail/domain.tld/username/cur/
5. When I try to send an email from RoundCube from and to the same email ([email protected]), I compose it, with dummy subject and body, and send. RoundCube displays the "Sending Message...", and after sometime the message disappears, but the composing message is not switched tot the Inbox, and just remains in composing mode.
6. A new email file appears in /homes/vmail/domain.tld/username/new/, but no new email shows up in Inbox in RoundCube.
7. When I click on the Inbox to refresh, no new email show up, but the file in /homes/vmail/domain.tld/username/new/ moves to /homes/vmail/domain.tld/username/cur/ (which explains the all files moving from Inbox after logging in).
8. mail.info has the record of the email being sent (status=sent delivered to maildir).
9. If I navigate to the Settings on Roundcube, and click on Junk (also have (Preferences, Folders, Identities, Responses, and Junk), the following error shows us:

DATABASE ERROR: CONNECTION FAILED!
Unable to connect to the database!
Please contact your server-administrator.

10. Trying to add a folder under the Folders in Settings does nothing. (Clicking on the + sign has no effect or result)
11. Clicking on any of the Section items under Preferences results in a "Loading..." that does nothing.

What did I try so far?

• I thought the file permissions under /opt/roundcube/ were off after upgrading, and in fact there was a mix of permissions there from Admin and www-data. So I ran chown -R www-data:www-data /opt/roundcube/ but that did not fix the outlined behvaior above.
• doveconf does have output mail_location = maildir:~/
• postconf output has home_mailbox = Maildir/

This is a DigitalOcean droplet, Debian 10, with multiple virtual users and virtual domains.

Any idea what could have went wrong after the upgrade/update?

Update 1 So an update, I looked into the warnings and errors in FireFox's console (press F12 to open), and I saw:

SecurityError: Permission denied to get property "href" on cross-origin object

and inside it

>     https://example.com/webmail/program/js/app.min.js?s=1577908851:127
>     msglist_select https://example.com/webmail/program/js/app.min.js?s=1577908851:107
>     init https://example.com/webmail/program/js/app.min.js?s=1577908851:42
>     triggerEvent https://example.com/webmail/program/js/common.min.js?s=1577908851:41
>     http_response https://example.com/mail/program/js/app.min.js?s=1577908851:337
>     success https://example.com/webmail/program/js/app.min.js?s=1577908851:330

I remembered that before the upgrade of the whole deal, I added a self-signed SSL certificate and had issues with it because of a PHP bug, and thats what triggered the whole Debian and PHP upgrade. I looked at the URL and it was a plain http://, so I changed it to https://domain.tld/ and now I can see all the email in the Inbox. BUT, after refreshing the page, all the emails are gone, and moved to the cur directory, and do not show up in the Inbox anymore. In addition, the Settings pages still will not load for me even with the https://

Answer 1

I ran grep -ri "X-Frame-Options" /etc/apache2 and found out that the SSL I self signed added this to the rule set.

I edited /etc/apache2/conf-available/ssl-params.conf and changed Header always set X-Frame-Options DENY to Header always set X-Frame-Options SAMEORIGIN. Saved the file, and restarted Apache (service apache2 restart) and now it shows the emails and settings.