Web Login Works Inside but not Outside

Steps to reproduce

1.Go to main login page (domain.com/owncloud)
2.Try to login using valid credentials
3. (login works within network (192.168.1.x) but not outside the network (mydomain.com/owncloud))

Expected behaviour

Should have logged in

Actual behaviour

After submission, login screen reappears with no error messages

Server configuration

Operating system:
Linux - ClearOS

Web server:
Apache

Database:
MySql

PHP version:

ownCloud version: (see ownCloud admin page)
Can't get to admin page either - unable to find password using defaults

Updated from an older ownCloud or fresh install:
fresh

Where did you install ownCloud from:
ClearCenter

Signing status (ownCloud 9.0 and above):

Login as admin user into your ownCloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results into https://gist.github.com/ and puth the link here.

The content of config/config.php:
<?php
$CONFIG = array (
'log_type' => 'syslog',
'datadirectory' => '/usr/clearos/EXTRA-DRIVE/data/',
'updatechecker' => false,
'check_for_working_htaccess' => false,
'asset-pipeline.enabled' => false,
'assetdirectory' => '/var/lib/owncloud',
'preview_libreoffice_path' => '/usr/bin/libreoffice',
'apps_paths' =>
array (
0 =>
array (
'path' => '/usr/share/owncloud/apps',
'url' => '/apps',
'writable' => false,
),
1 =>
array (
'path' => '/var/lib/owncloud/apps',
'url' => '/apps-appstore',
'writable' => true,
),
),
'dbtype' => 'mysql',
'dbname' => 'owncloud',
'dbuser' => 'owncloud',
'dbpassword' => 'KNdloxxxxxIOIBo',
'dbhost' => '127.0.0.1:3308',
'dbtableprefix' => 'oc_',
'instanceid' => 'oc5nz65ow31g',
'passwordsalt' => 'ZIpCsmUCvBxxxdZ84aUAYA75KVL',
'secret' => 'rqgpqDA480d0YBJtpgfOxxxKGVgdbgKghXn2ZUj6Yj',
'trusted_domains' =>
array (
0 => 'xxxx',
1 => '6xxx6',
2 => '10.50.100.1',
3 => 'globaXXXXte.com',
4 => '',
),
'overwrite.cli.url' => 'http://localhost/owncloud',
'version' => '8.2.4.2',
'logtimezone' => 'UTC',
'installed' => true,
'ldapIgnoreNamingRules' => false,
);

Log in to the web-UI with an administrator account and click on
'admin' -> 'Generate Config Report' -> 'Download ownCloud config report'
This report includes the config.php settings, the list of activated apps
and other details in a well sanitized form.

or 

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your ownCloud installation folder

*ATTENTION:* Do not post your config.php file in public as is. Please use one of the above
methods whenever possible. Both, the generated reports from the web-ui and from occ config:list
consistently remove sensitive data. You still may want to review the report before sending.
If done manually then it is critical for your own privacy to dilligently
remove *all* host names, passwords, usernames, salts and other credentials before posting.
You should assume that attackers find such information and will use them against your systems.

List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your ownCloud installation folder.

Are you using external storage, if yes which one: local/smb/sftp/...

Are you using encryption: yes/no
no

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...
LDAP

LDAP configuration (delete this part if not used)

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your ownCloud installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM `oc_appconfig` WHERE `appid` = 'user_ldap';


Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

Client configuration

Browser:

Operating system:

Logs

Web server error log

Insert your webserver log here

ownCloud log (data/owncloud.log)

Insert your ownCloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log 
c) ...

Maybe check your logfiles? (Logs part of your posting)