Mac does not switch automatically between dark and light modes

My Mac was turning dark and light modes automatically, but it doesn’t anymore. Night shift works, but it stays dark or light unless I cycle the options in System Prefs. I changed nothing since I bought this Mac. Why could this be happening?

Hey there!
Maybe it could be by the update to catalina
Check the solution in this link
https://m-mx.gearbest.com/blog/how-to/macos-catalina-automatic-darklight-mode-not-working-try-these-solutions-8767