Hi. I'm David, and I'm happy to help you.
This is typically a temporary issue that can arise for various reasons, including potential problems with your internet service provider (ISP).
Try using a different browser.
If you cannot use a different browser, see if the same behavior occurs in an InPrivate/Incognito window.
To open the InPrivate/Incognito window, open the browser and press "Ctrl + Shift + N". (For Microsoft Edge and Google Chrome)
If you still can't download the ISO, let me know in which language you need the ISO, and I will provide a direct link.
Feel free to ask back any questions.