I have no idea how to troubleshoot this. Manually suspending works, and it suspends automatically usually about 1 - 2 days after rebooting, then suddenly even the screen won’t turn off.
What DE are you using? I noticed that under XFCE, I have to use the display-managed suspend option, rather than the “system-managed” one (not sure why there’s a distinction).
i use cinnamon. and every suspend option works when done manually in terminal or gui.
That seems like a policy kit issue. Maybe the system doesn’t have the permissions to do it automatically. XFce usually has such problems in other distros, but I haven’t heard one on mint with cinnamon.
Another thing to look at is what graphics card you’re using. With nvidia you can get some weird suspend issues.
Finally, install a newer kernel to see if that fixes the issue.
Do you have steam running? Lately it’s been blocking sleep after even just sitting in the tray for me. This is on arch kde.
