The WHMCS addon for Website panel V1.2 seems to have a bug in it.
If you keep getting WHMCS Addon Not Found! Check The ID And Try Again. and you know the ID’s are correct.
Check modules\addons\websitepanel_addons\websitepanel_addons.php
Line 148 show look like this
$results = select_query(‘tbladdons’, ‘id’, array(‘id’ => $_POST[‘whmcs_id’]));
not this
$results = select_query(‘mod_wspaddons’, ‘id’, array(‘id’ => $_POST[‘whmcs_id’]));