Shortcuts not working. “File” highlights

I am trying to use ^T (Control T) and ^W (Control W) for “New Tab” and “Close Tab” respectively in my web browsers. The shortcuts are listed correctly in “Keyboard > Shortcuts > App Shortcuts > All Applications”. When I try to use them, the “File” menu in the bar at the top is briefly highlighted with a blue highlight, then it becomes unhighlighted and nothing happens after that. Command+T and Command+W still manage to successfully open and close tabs. What am I doing wrong?