I've looked into this and have been informed by the team that this was an issue today which unfortunately affected the download service. This has persisted for approximately 1 hour today before getting solved, so you should be able now to export.
Could you please retry downloading your assets and see if it succeeds?
Thanks a lot, we're very sorry for the inconveniences! Madalin
Could you please provide more details into what you're trying to download (is that a video or other type of document)? Also, any details about your environment could help (what is the browser type/version that you use, what OS, etc).
Thanks a lot, providing more details here could help us pinpoint a solution. Please also refer to this page for details around what system requirements are recommended.