https://wccftech.com/warcraft-iii-reforged-update-1321-download-issues/

The launch of launch of Warcraft III: Reforged didn’t quite go as planned. Changes to rules regarding mods, removal of fan-favorite community features, a visual makeover that was less impressive than originally promised, and a boatload of glitches led to a mass revolt from the game’s fans, but Blizzard is promising to bring things up to snuff. As part of that, the first major Warcraft III: Reforged update has been released, and well...I’m going to guess most fans were hoping for more. The update mostly focuses on fixing various bugs, although the visuals and UI for Classic Mode have also been tweaked.

Of course, since seemingly nothing related to Warcraft III: Reforged can go right, a number of people are having trouble downloading the new update, and as this is a required patch, it’s rendering the game unplayable. Whoops! That said, based on comments on the Blizzard forums, it seems like most people are resolving the download issue by simply restarting Battle.net, although some are still having issues even after doing so.