Late 2012 iMac not restarting or shutting down

Many thanks for your response ku4hx,

I should have been clearer and said "I'd still like to self-diagnose the issue" (with the help of any knowledge that these forum members might have in relation to my points about looking logs and replacing the power supply).

Basically I'm curious to see if anyone else has experienced this same issue, and if so, were they able to self-diagnose the issue looking in the Console logs (or other logs), and is this something that a power supply replacement might fix.

I have found lots of posts with what sound like similar issues (some below), however they all only suggest the SMC/PRAM/Safe Mode/reinstall macOS options that I have already tried (none mention replacing power supply in the machine) - I thought that a forum member might know (from a technical point of view) if replacing this would likely fix this issue (I am sceptical because the machine turns on fine, just doesn't shut down/restart, however this goes back to my issue with the logs and not being able to see any clues as to the cause).

My iMac won't shut down - Apple Community

macOS Catalina does not shut down - Apple Community

Mac won't shut down or restart after Sier… - Apple Community

Mac won't restart or shut down - Apple Community

Many thanks

Hi,

This issue was resolved when I removed the iMac's internal HD whilst trying to fix another issue. It now shuts down and restarts as normal.

Many thanks

Many thanks for your reply MVegas21.

I have just contacted Apple Support and they advised that I have already tried everything that they would suggest, therefore I should book in to see a technician. I may do this if I truly exhaust all of my options, however if possible I'd still like to diagnose the issue, my main concern is that I can't see any clues in the Console logs to confirm whether this is a hardware issue or not (also, I don't know exactly what I'm looking for but can't see anything relating to shut down/restart).

If it is a hardware issue, would opening up the iMac and replacing the power supply be a possible fix?

Many thanks

I have just tried the 'sudo shutdown -r now' command in the terminal. When I hit enter it made the 'not allowed'/'error' sound twice, and showed the following in the Console:

error	13:05:08.359731+0100	Terminal	AddInstanceForFactory: No factory registered for id <CFUUID 0x6000017ec9a0> F8BB1C28-BAE8-11D6-9C31-00039315CD46
error	13:05:08.373903+0100	Terminal	 HALC_ShellDriverPlugIn::Open: Can't get a pointer to the Open routine
error	13:05:08.374416+0100	Terminal	 HALC_ShellDriverPlugIn::Open: Can't get a pointer to the Open routine
error	13:05:08.374880+0100	Terminal	 HALC_ShellDriverPlugIn::Open: Can't get a pointer to the Open routine

Please has anyone ever seen this before?

Many thanks