I recently upgraded my 2018 Mac mini to macOS Catalina 10.15.6, and I’ve noticed that whenever I turn my monitors off and leave my computer, it never actually locks itself after the 10 minutes when it’s left alone. Is there any way to fix this? I can manually lock the screen and make it go to sleep but that’s kind of a pain to do every time I want to leave my computer.
Check the battery settings in the Energy Saver. You should be able to see a dial to change the time needed for your Mac to sleep. The defaults for these have been known to change from time to time, so you may be able to put it back to what it was originally.
Incidentally, locking your computer by leaving it unattended for 10 minutes is not a good security practice. If you want a quick way to lock it, see here for sleeping and here for locking. This is a habit that is worth picking up.