I don't see how could MonitorControl prevent the mac from sleeping. You can check out what is preventing sleep by looking at the Activity Manager's Energy tab and see the Preventing Sleep column.

Hey @dtsimon - let me know if you see anything - does the app prevent sleep according to the Activity Manager? Should I keep this issue open? Thank you!

I'm experiencing the same exact issue with Version 4.0.2 Build 6965 running on a M1 with macOS Big Sur 11.6 . I must remember to slide the control to full brightness so that sleep will work. As mentioned above, the Aerial screensaver seems to have found a temporary workaround for perhaps the same bug - https://github.com/JohnCoates/Aerial/releases/tag/v3.0.8beta1 .

Same thing here for version 4.1.0 Build 7034. On an M1 16in MBP running Ventura 13.0.1.
Easy steps to verify:

• Put the computer to sleep and swipe on the trackpad, the computer wakes because it's not sleeping.
• Quit MonitorControl and do the previous step again. Swiping the trackpad won't wake the computer because it's actually sleeping.

Macbook Air M1 8/256 with Sonoma 14.1.2 (23B92), current version of MonitorControl as of 2023/12:
Same problem here. Macbook either does not go to sleep or wakes up a few minutes later when MonitorControl is running. Everything working fine when MonitorControl is closed.
A real shame because the program is simple to use, good-looking and really useful.

Not sure whether this is still an issue. You can check what app prevents sleeping in Activity Monitor or by entering this in Terminal:

pmset -g assertions

Normally the app should not prevent sleep (there is nothing in it that should interfere afaik).