Chrome extension: Could not load javascript file

I took a look inside your extension's ZIP file before downloading it, and the result was the following:

^{*Inspected using Chrome extension source viewer by Rob Wu}

The problem here, is that you've uploaded a packed CRX file inside of your ZIP file, instead of your extension source code. You should instead upload a ZIP file containing your extension's root. Since that you're including the manifest.json file, the Web Store doesn't notice anything wrong until you try to install the extension, because the manifest is well written, but when Chromes tries to access the files declared, it fails and returns an error, because those files do not exist.

Quoting from the upload page of the Chrome Web Store Developer Dashboard:

Uploading an item:

• Upload a ZIP file of your item directory, not a packaged CRX file.
• Include a well-designed product icon in your manifest (more info).
• Read the documentation about creating and packaging apps.
• Need more help? Check out the Chrome Web Store developer documentation.

So, you should create a ZIP file of your extension's root directory, containing all the files of your extension. Your ZIP file should then look like the following: