Text not displaying in Storyline project

I have created a Storyline project & distributed through our LMS. The project includes text, images & audio in the form of narration.

Initially the course worked well with all users able to view all elements & complete sucessfully. However after a few months the project took ages to load. Some couldn't access at all & some could just see the 'spinning wheel' that displays when a project is loading. Others could hear the audio & see the images, but the text wouldn't display.

I have tested this at home (external to our network ) & the project played without any problems.

I then republished the course & updated the training schedule which appered to resolve the issues, however these have now resurfaced after a month or so.

There is obviously an issue with our network. I am hoping to gain some advice from others who have encountered a similar issue & the resolution. I am thinking software update &/or firewall config?

Regards,

Brad