Tom can't open anything on his Chrome browser, especially in Gmail. Leo says that Chrome can do this from time to time. He should try resetting his browser. He'll find it in the settings menu. That will clear out the cache. This article at support.google.com will show him how.
If that doesn't work, Tom can try downloading a new version of Chrome. He should first uninstall the old version and then reinstall it. He can also try logging in with another account. If that works, then there's an issue with his Google account.