You can do this by going to Seller Admin > Re-activate expired links & Re-send Thank-You Email, where you will need to enter your Transaction ID for the order, which you can obtain from your PayPal account history or receipt email, or from your E-junkie Sale Notification email or Transaction Log.
You may also reactivate links directly from within your Transaction Log by using the green Reactivate Links button available under the Transaction ID for each entry in the log.
You can reactivate expired download links up to a maximum of 5 times per transaction. This resets the Attempts and Hours (if applicable) countdown on each link issued for the order, according to your product settings for those items, as if the link(s) had just been issued when you reactivated it. Your Transaction Log will only show Attempts made on the link since it was last issued or reactivated.
If you have already reactivated a link five times and need to do so again it is still possible to use the Send Free Download Link/Code screen as an alternate way to provide a buyer with a new download link.