Please check article where is described how you can download EXOS firmware.https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-get-access-to-Extranet-for-for-firmware-and-configuration-guide-downloads/?q=download+exos&l=en_US&fs=Search&pn=1
We're going to need more information on this. The download command will eventually time-out if there is a problem.
What is the exact command are you using to download the image? What's the error displayed after the time-out?