Hi Tanya,
If your course doesn't launch properly for certain users, try asking them to clear their browser's cache, or asking them to use a different browser to see if this helps.
Additionally, you can test your course in SCORM Cloud like what my colleague John mentioned to isolate if the issue is LMS specific. Here's how. Lastly, if you think that the course is somehow being blocked by the network, your users will need to reach out to their network admin to add the URL of your course to their network's allowlist for your course to open properly.