Some electronic resources to which the Library subscribes make extensive use of pop-up windows, where the resource generates a new browser window.
Normally, the new window appears as the active window, so that you can see and deal with its content.
In some cases, the browser blocks the pop-up window.You see a "blocked pop-up" message and a yellow bar at the top of the browser.
Close the message window, click on the yellow bar and choose "always allow pop-ups from this site". You may need to shut down all open browser windows and start again.
In some cases the pop-up window appears underneath another window so is not visible and it seems that nothing has happened. Minimise all open windows until you can then restore them in turn to find the one you want.