Displaying Pictores & PDF Files in Robohelp

Hi,

I am currently using an older version of Robohelp 6 & have it hosted on the company's intranet site.

I've had no issues with displaying pictures &/or PDF files on the site

Recently when employees were trying to access site some pictures would not display (just show box with X) & same is for the PDF files as well.

Does anyone know what might be the issue?