Hi Chris

There was some discussion on this on https://totara.community/mod/forum/discuss.php?d=16820#p2058 as below hopefully this helps.

Captivate 5 has a number of bugs that have caused problems. Including SCO activities getting stuck on the gray loading page. 

This is a problem in how Captivate communicates with Totara.

It is fixablable:

1. Publish the Captivate file as SCORM.
2. Open the HTML wrapper file with the same name as your course.
3. Find the following line of code:
   1. strURLParams += (strURLParams==""?"?":"&") + "SCORM_API=" + g_zAPIVersion + "&SCORM_TYPE=" + g_intAPIType;
4. Change the line of code to:
   1. strURLParams = "?SCORM_API=" + g_zAPIVersion + "&SCORM_TYPE=" + g_intAPIType;
5. Save the HTML file and zip up all the files.
6. Upload zip to LMS.

See this blog for more information: http://thedesignspace.net/MT2archives/000826.html

Craig