You edit a package, change Module from cPanel to cPanel Extended.
You then log in as the client, click any of the tabs, none of them work.
Cancel the service (Not using the cPanel module).
Then re-add the service using the new package, everything works.
EG: http://www.blesta.com/forums/index.php?/topic/826-cpanel-extended-for-blesta/?p=8366
Fix: http://www.blesta.com/forums/index.php?/topic/826-cpanel-extended-for-blesta/page-3#entry8613