Hi Jon, the most common reason for this is that the changes have been added to a different version than you expected.
If this isn't the case please could you supply the page your trying to use the web companion on.
As Simon mentions, the most common reason is that you're already logged into the UI. If you are already logged into the UI when you save from Web Compaion you will need to log out and log back in for the new version from Web Companion to be pulled in.
Also, You need to make sure to push the changes into the UI from the Queue found at the bottom of Web Companion. When you add something from Web Companion you've got to make sure to hit save. It will then ask you to login and save to profile. Once that is complete the changes should get pushed to into the UI.