Resolved Mac won't go to sleep

[Silly John Fatty]

When I do the shortcut or when I go in the Apple Menu and put it to sleep, the screen turns black, but the Mac doesn't go to sleep.

Quit all apps, restarted it multiple times. Checked activity monitor (there's two sleep-preventing processed, cupsd and hidd. Sometimes there's also mds_stores or apsd, but these are all necessary/normal I believe). What else could cause this issue?

It's a mid 2010 Mac Pro and I have the 27 LED Cinema Display.

I didn't reset the NVRAM (or PRAM?) yet, because I don't know if you can do this with the GPU that I have (it's a RX 580).

 

[TimmuJapan]

Which version of macOS are you using?

I think that your first step should be to reset the NVRAM and the SMC.

 

[Silly John Fatty]

Which version of macOS are you using?

I think that your first step should be to reset the NVRAM and the SMC.

I managed to fix it, cupsd was the problem. I couldn't really quit the process, but I had to open the printer app and there was something waiting to be printed in queue. So I removed that and then it worked, I could put the Mac to sleep.