Hello.

Nothing was changed on the system, but now the screensaver does not work anymore. Thus, no more is calculated for the project "Seti at Home" if the computer is unused. It looks like the screensaver is not started because it thinks that the computer is in use. This is recognizable because the screensaver does not even start when you go to Settings - Lock screen - Settings for screen saver preview. I've already tried if the available beta version does that better, but it has the same problem. The system has not changed, the problem occurred suddenly and out of the blue. Who ever had the same problem and can help?

Whether the computer is Idle or not is determined by the OS. BOINC does not determine if the computer is idle or not. So something else is keeping your computer from being idle and the screensaver from running.

The user did not post whether the following was of help: https://boinc.berkeley.edu/dev/forum_thread.php?id=12362&postid=85380. From their silence, it could be assumed it was

Game controllers can also give false positives when plugged in and idle.

It would appear you have recently installed a GPU (nVidia GTX1080ti) in your system. The GPU applications for SETI do not contain the code for the screen saver, so it doesn't appear any more. Looking at the stats for your computer it is running, and has been returning work fairly freely recently.