There's a few things that might be causing your build/upload to get stuck or hang.
If you're stuck on uploading, its possible that your ISP has bad routing to the content servers, or your connection is being filtered/throttled. The best solution we can offer at this time is to suggest using a VPN. Usually these are paid services. We suggest trying VyprVPN or PrivateInternetAccess.
If you're having build errors, check your Unity Console for errors. If you can't figure out the errors, shoot an email to email@example.com.
Worlds can also hang on building if you forgot to uncheck "Auto Generate Lighting" in your Lighting tab. Make sure you perform lightmap baking before clicking "Build and Publish" in the VRChat SDK.