Mac Dark Mode keeps resetting to the standard light mode.
For those who like to use Dark Mode, you might become frustrated each time you return to your Mac, and it's reset itself back to Light Mode.
It can happens after, Reboot, Wake up, Starting an app that uses fullscreen mode
3rd Party Conflict
One of the most common problems with this is a third party application that uses night shield-like Flux and Nightowl.
You can turn them off, or change the setting to prevent this conflict.
After a quick search online I couldn’t find any really helpful answers without spending an hour trawling through comments on forums