I have my screen saver to come on after 1 minute of no activity. It will not come on by itself. I have tried rebooting the whole system to be sure. I implemented a Hot Corner so I could manually put my screen to sleep. It sleeps and then wakes back up in 10 seconds. I am afraid I will ruin the screen by it being on all the time and I have run out of things to do about it.
iMac Line (2012 and Later)
To trouble shoot further you can:
Try a SafeBoot https://support.apple.com/en-us/HT201262
Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc. Login and test. Reboot and test will take a little longer as caches get rebuilt.
This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.
Test issue in another user (or guest user) account https://support.apple.com/en-us/HT204443
This will tell you if it a universal issue or isolated to your user/admin account.
First you are not going to ruin your screen.
That aside, follow the great suggestions you already got and tell us the results.
Also run Etrecheck and post its full report here for us to look for possible suspects.
screen saver not working
