@
seanj1 - there are quite a lot of different reasons for this happening, and as it isn't a general game problem, each one tends to need individual troubleshooting. If you start your own thread and give more details, someone should be able to help you. In most cases, we've found specific reasons why it isn't working, it's just a few that are making everyone scratch their heads.
Please include full system specs, whether it's Gog or Steam, and what you've already tried.
Thanks.