Screen stays on past timeout settings

I have my screensaver set to come on after 20 minutes of inactivity and my display set to turn off after 30 minutes. I leave my Mac running overnight and I was surprised this morning to see that the screen was still on, and must have stayed on all night. This issue has just started and I've not made any changes to my system. The most recent macOS update was a week or so ago to 15.6.1 and this problem just started yesterday. I use a Dell S2722DZ display and I don't see any of its settings that would override the OS settings. Any suggestions as to why the OS seems to be ignoring my settings?