screensaver not coming on

Diagnosing a Mac that won't sleep can be time-consuming. It is always due to a process keeping the system awake, but determining which process or processes is the challenge. The following is a list of troubleshooting techniques I have complied over the years.

• A first simple step is to create a new, temporary user account: How to test an issue in another user account on your Mac - Apple Support
  • Log out of your usual Account, and log into the temporary one. Determine if it sleeps then.
  • If it does, then you may have a Login Item that is preventing sleep. System Preferences > Users & Groups > Login Items.
  • To remove the temporary User Account read macOS Sierra: Delete a user or group.
• Whenever you suspect a problem related to power, including sleep, an SMC reset is also recommended.
• Active Spotlight indexing will prevent sleep. Wait for it to complete.
• Check your Sharing preferences for anything that could permit an active network connection.

  Toggle each one individually, followed by sleeping the Mac after each inversion.

• Energy Saver "Wake for network access" can prevent sleep, but unchecking it will prevent the ability to remotely access a sleeping Mac over a network.

  A normally functioning Mac will sleep according to Energy Saver, but will wake periodically for network access, after which it will return to sleep according to the settings in Energy Saver.

• Check Energy Saver > Power Nap. Whatever its setting happens to be, change it.

  Power Nap itself does not prevent sleep, but a corrupted Power Nap setting might. Changing its setting might correct it. Test, and then revert the change.

• Unfinished print jobs will prevent sleep. If a print job is queued, but if the printer is off or the connection to it is lost, the Mac will stay awake forever waiting for the printer to return.

  To reset the printing system (which will kill unfinished print jobs) read macOS Sierra: Reset the printing system.

• Safari pages that periodically refresh themselves are very common. This will prevent sleep.
• Frequently checking for new mail may prevent sleep. If applicable, change Mail's Preferences to check for new mail less frequently.
• iTunes and Photo sharing services will prevent sleep.
• Active Bluetooth devices will prevent sleep.
• Active USB or Thunderbolt devices will prevent sleep. Disconnect them to help isolate the cause.
• Using Time Machine over a network may prevent sleep. Time Machine using a Time Capsule will not.
• There are plenty of third party utilities designed to prevent sleep. One may not have been completely uninstalled.
• Try quitting the process with the name powerd in Activity Monitor. It will re-launch on its own.
• Any number of non-Apple "anti-virus" utilities can prevent sleep as well as cause other miseries. Get rid of them.

To diagnose sleep problems temporarily set Energy Saver to sleep after the minimum amount of time (one minute). When you believe the system should be sleeping but it's not, run the following bash shell script.

clear; printf '\e[3J'; P='pmset' Q=(Events Thermal Load Assertions Preemptions) R=(0 therm sysload assertions 4) S='\n####'  T=$(pmset -g | grep -o "sleep prevented.*[^)]") ;  printf $S\ ${Q[0]}'\n' ; log show --style syslog --last 24h | egrep -i 'system\ sleep|system\ wake' | egrep -i 'PMRD' | egrep -v can | awk -F']' '{print substr($0,1,19), $NF}' | tail -n 12 ; log show --style syslog --last 24h | egrep -i 'Wake\ reason:' | awk -F']' '{print substr($0,1,19), $NF}' | tail -n 12 ; printf $S\ ${Q[1]}'\n' ; $P -g ${R[1]} ; printf $S\ ${Q[2]}'\n'; $P -g ${R[2]} | tail -n +3 | awk '{print $1, $2, $NF}' ; $P -g batt ; printf $S\ ${Q[3]}'\n' ; $P -g ${R[3]} | tail -n +14 | grep id | awk '{print $1, $2, $NF}' ; printf $S\ ${Q[4]}'\n' ; if [ -z "$T" ]; then echo None; else echo $T; fi 2>&1

To use it launch Terminal—it's in your Mac's Utilities folder. Copy the above line (triple-click to select the entire line) then Paste it into the Terminal window. After a few moments the script will respond with its results.

For interpretation, Copy (Edit > Select All, then Copy) and Paste its contents in a reply to this Discussion.

Please read If your Mac doesn't sleep or wake when expected - Apple Support. The most applicable steps are likely to be found under "If the previous steps don't work." Follow each of those steps.