You're definitely building your distribution incorrectly.

From the Ren'Py launcher (latest version), select your project but don't click Build Distributions.  Instead, click Web (Beta), then Build Web Application.  This creates a directory with a bunch of stuff including a game.zip file.  Ignore everything else and upload the game.zip file.  Correction: you need to upload the entire directory, packaged as a zip file.

The Build Distributions button is for building downloadable games, not web games.