Welcome to the forum.
Usually, when that happens, it is due to one's account, or perhaps a firewall/security setting.
As a test, Export/Share to the format for the Web host, and then manually upload that with your account. Does that work?
Good luck, and let us know how the test goes.
Until you can figure it out, you can always manually output a video and upload it yourself. Many people prefer this method since it often gives you a much better quality video.