We have a few machines that will not stay connected. They are all running the latest version, 2.8.1. We didn’t have an issue until updating.
Explain what do you mean. Are they not able to connect at all or do they connect and then disconnect after some time (or keep reconnecting)? What version exactly was working ok before? If you go back to that version, does it work fine? Have you tried rebooting your server? Maybe something in the logs at c/users/user/appdata/spark/logs?