Please verify that you have cookies enabled and that you have no other browser extensions installed that may block communicating with the Shelf servers.
You can also enable cookies specifically for our Web Clipper, in case you want to continue blocking other sites' cookies.
In order to do so, navigate your Chrome browser to chrome://settings/content/cookies (you can copy paste the link into your browser location bar) or alternatively, select "Preferences/Settings > Advanced > Privacy and security". Find the section "Content settings > Cookies".
Add the Shelf Web Clipper in the "Allow" section, using this URL: chrome-extension://heaabifmflabgcllpdefnkafcookcbji/ (this is the Web Clipper Extension Id assigned by the Chrome Store).