>This is and old issue that I have asked before but have not been successful in finding an answer.
>
>I have a global timer in my app to monitor the app status. On some machines the app seems to go to sleep, the timer stops firing. If I start interacting with the app on these machines the timer will usually start firin again. I have noticed the interaction has to be more than just opening and closing forms. Not really sure what is going on.

This is a SWAG, but check that devices are not being powered down after some inactivity time. You'll need to check in the computer's BIOS, as well as Windows' power settings.

For machines that run 24/7 generally you want to turn off or disable all power saving features, except perhaps for the monitor, which could be set to go off after 20 minutes or so (might be the default scheme under Windows).