Hello,
as stated in https://moodle.org/mod/forum/discuss.php?d=230418 :
"For the external package type to work – your SCORM content MUST be located under the same url as your Moodle site – If the base url is different from your Moodle url then built in web browser security will block cross-domain communication and no grades/tracking information will be passed back to Moodle. Adobe Flash and modern browsers (ever since IE 6) prevent cross-domain communication. If you really need your packages to sit outside Moodle on a different URL you should look at other options for hosting your content."
I would try to enable some subdirectory inside your main domain, something like http://DOMAIN/shared or something.
Best,
Raúl