There is an ongoing issue with Microsoft Imagine Academy webstore. Some products yield erroneous download links which result in 403 Forbidden error messages. MS Imagine webteam at Kivuto is looking into the issue and hopefully it will be resolved soon.
UPDATE 21.9.2017! So far it seems this is a problem limited to Funet and Telia customers, so as a workaround you should try downloading your products from a different network if possible.
REMINDER: Seeing as this is *still* an issue, we would like to remind you that you will still get valid licences through Imagine Academy. You can obtain the installation media elsewhere. One example is the Windows 10 media creation tool Microsoft offers.