If you are a regular user of Web of Science but are having difficulty accessing it now, it may be because of a change in the default user interface. What used to open in Advanced Search now defaults to Smart Search. If you see a gray overlay with a message like “Welcome to Smart Search,” simply click the X in the upper right corner of that box. Then, click the Advanced Search tab at the top left of the screen to return to the interface you're familiar with. Your access remains unchanged—just the look and layout have been refreshed.
If you try this and continue to have access issues, please contact a librarian.