Please describe your issue in more details.
Which exact version of LR are you using and on which OS?
Lightroom 2015.6.1 versie Lightroom cc
OSX El Capitan
To what website are you uploading the pictures? Are you behind a (corporate) firewall, blocking certain activities?
You didn't describe the issue in more detail. Guesswork can be shortened a lot, when you describe how you proceed to download to the web. Please add screenshots where applicable.