You have the wrong version of ioncube for your server or PHP.ini isn't configured properly causing a silent server error and preventing ioncube from loading and working correctly. This has been answered over a dozen times, please contact your host as they're responsible for configuring ioncube for you or at least providing instructions as to how.

Then you've a php.ini configuration issue or you have not placed php.ini in Joomla root and root/administrator. If is placed in the correct locations then it's probably a configuration issue where php.ini is trying to load PHP extension that don't exist. If you're on hostgator they're famous for providing a bugged php.ini and I've had to fix it 3 times on users installs; please review the below topic.

www.joomlapolis.com/forum/153-professional-member-support/212054-solved-cb-subs-corrupted-message?limit=6&start=6#212738

Another similar issue can be found below.

www.joomlapolis.com/forum/153-professional-member-support/192230-solved-500-error-when-i-click-on-configuration#192276

Another as follows.

www.joomlapolis.com/forum/86-cbsubs-paid-membership-management-solution/184695-problems-installing-cb-subs?limit=6&start=6

Please understand I can't keep fixing issues caused by bad hosting, pick your hosts more carefully that can provide a working experience; they should easily be able to see the extension load failure in their server logs.