really.....check your settings and make sure that you are not trying to use some other dimension tool.....I had trouble with my short cut key but it started working. Think that it was a user error I was hitting the wrong key.....or hitting 2 of them....I think that they are making the keyboards smaller or something...
I face this issue when I was using very low configuration workstation. SW will required atlease 8GB RAM and a graphics card. If you don't use them, then you might face this short of issue. What is your system's configuration? Also try resetting your system options.