Static sites will not resume downloads. You need to use 3rd party software or Addon that can resume downloads properly.

''<p>mike_coreit [[#question-1408947|said]]</p>'' <blockquote>Hi I'm trying to download large files but they keep failing due to problems at the host. I can resume the download when this happens but I don't want to keep doing this. Is there any way to auto-resume? </blockquote> The server may not support resume if you can't continue the download. from [/questions/1385732#answer-1526272] <blockquote>The usual procedure where you want to resume an interrupted download is as follows: Make sure to backup the .part file and the final file with size 0 without the .part before starting Firefox. Try these steps to resume an unfinished download if you still have the .part file. # Move the old .part partial download and the final file without the .part that has size 0 to another location. # Start a new download and pause it, don't close Firefox. # Copy the two files (.part and 0 byte final) that you moved above back to the download location to replace the new files that were created. # Resume the download in Firefox. If that doesn't work then the server may not support resuming. Best is to use an external download manager to prevent issues with paused or interrupted downloads. </blockquote> https://support.mozilla.org/en-US/kb/cant-download-or-save-files