After a freshly installed WHMCS installation I cannot activate the addons, and those addons are the ones that come with WHMCS, so only official addons are installed, take a look at the picture.
The Apache2 is running with SuexecUserGroup
apache -v
Server version: Apache/2.4.10 (Debian)
Server built: Mar 15 2015 09:51:43
$ php -v
PHP 5.6.7-1 (cli) (built: Mar 24 2015 12:30:15)
Copyright (c) 1997-2015 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2015 Zend Technologies
with the ionCube PHP Loader + Intrusion Protection from ioncube24.com v5.0.4, Copyright (c) 2002-2015, by ionCube Ltd.
with Zend OPcache v7.0.4-dev, Copyright (c) 1999-2015, by Zend Technologies
$ stat addons
File: ‘addons’
Size: 4096 Blocks: 8 IO Block: 4096 directory
Device: fe01h/65025d Inode: 914806 Links: 12
Access: (0755/drwxr-xr-x) Uid: ( 1001/ msp) Gid: ( 1001/ msp)
Access: 2015-05-16 13:12:37.825522766 +0000
Modify: 2015-05-16 13:05:54.840028312 +0000
Change: 2015-05-16 13:12:31.625499954 +0000
Birth: -
$find . -type f -printf "%f:%p:%u:%g:%m\n"
hooks.php:./licensing/hooks.php:msp:msp:644
licenseverify.tpl:./licensing/licenseverify.tpl:msp:msp:644
licensing.php:./licensing/licensing.php:msp:msp:644
ajaxCreateWHMCSAccount.php:./plesksync/ajax/ajaxCreateWHMCSAccount.php:msp:msp:776
ajaxImportPleskAccount.php:./plesksync/ajax/ajaxImportPleskAccount.php:msp:msp:776
ajaxGetServerStats.php:./plesksync/ajax/ajaxGetServerStats.php:msp:msp:776
ajaxGetPleskAccountDetails.php:./plesksync/ajax/ajaxGetPleskAccountDetails.php:msp:msp:776
ajaxCreateWHMCSOrder.php:./plesksync/ajax/ajaxCreateWHMCSOrder.php:msp:msp:776
ajaxChangeStatusInPlesk.php:./plesksync/ajax/ajaxChangeStatusInPlesk.php:msp:msp:776
wait_import.gif:./plesksync/images/wait_import.gif:msp:msp:776
wait_details.gif:./plesksync/images/wait_details.gif:msp:msp:776
plesksync-icon.png:./plesksync/images/plesksync-icon.png:msp:msp:776
Whmcs.Api.class.php:./plesksync/Whmcs.Api.class.php:msp:msp:776
plesksync.php:./plesksync/plesksync.php:msp:msp:776
config.php:./plesksync/config.php:msp:msp:776
.DS_Store:./plesksync/.DS_Store:msp:msp:776
README.txt:./plesksync/README.txt:msp:msp:776
plesksync.class.php:./plesksync/plesksync.class.php:msp:msp:776
enom.gif:./newtlds/images/enom.gif:msp:msp:644
ico-info24x.png:./newtlds/images/ico-info24x.png:msp:msp:644
newtlds.php:./newtlds/newtlds.php:msp:msp:644
hooks.php:./newtlds/hooks.php:msp:msp:644
english.php:./newtlds/lang/english.php:msp:msp:644
newtlds.tpl:./newtlds/newtlds.tpl:msp:msp:644
google_analytics.php:./google_analytics/google_analytics.php:msp:msp:644
hooks.php:./google_analytics/hooks.php:msp:msp:644
addonexample.php:./addonexample/addonexample.php:msp:msp:644
hooks.php:./addonexample/hooks.php:msp:msp:644
english.php:./addonexample/lang/english.php:msp:msp:644
jquery.staffboard.js:./staffboard/js/jquery.staffboard.js:msp:msp:644
jquery.staffboard.css:./staffboard/css/jquery.staffboard.css:msp:msp:644
hooks.php:./staffboard/hooks.php:msp:msp:644
staffboard.php:./staffboard/staffboard.php:msp:msp:644
eu_vat.php:./eu_vat/eu_vat.php:msp:msp:755
hooks.php:./eu_vat/hooks.php:msp:msp:755
spanish.php:./eu_vat/lang/spanish.php:msp:msp:755
english.php:./eu_vat/lang/english.php:msp:msp:755
paypal_addon.php:./paypal_addon/paypal_addon.php:msp:msp:644
hooks.php:./paypal_addon/hooks.php:msp:msp:644
index.php:./index.php:msp:msp:644
fixed_invoice_data.php:./fixed_invoice_data/fixed_invoice_data.php:msp:msp:644
hooks.php:./fixed_invoice_data/hooks.php:msp:msp:644
bulkpricingupdater.php:./bulkpricingupdater/bulkpricingupdater.php:msp:msp:644
style.css:./bulkpricingupdater/style.css:msp:msp:644
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Also one thing I forgot to add the screen is blank on Setup > Addon Modules, and the error logs don't show anything