This applies only to the desktop app. The web upload tool was not affected. Yesterday, certain servers had technical issues which affected connectivity for some users of the desktop app.
We apologize if you were affected by this issue. The web uploader was available for all users at this time.
We are still working to phase out some older-generation server code. We will post at this blog, and send an email out via our newsletter, once this is completed. Stay tuned.
Check out our team page to meet the people behind ShareByLink.