Drive Not Ejected Correctly.

Xabiablanca wrote:

Yes, but here is my screen shot of Energy Saver. Am I missing something, a switch somewhere or similar?

Not all hardware support this newer feature:

Which Mac computers can use Power Nap?

You can use Power Nap on these Mac models:

• MacBook (Early 2015 and later)
• MacBook Air (Late 2010 and later)
  Requires OS X Mountain Lion v10.8.2 and later
• MacBook Pro (all models with Retina display)
• Mac mini (Late 2012 and later)
• iMac (Late 2012 and later)
• Mac Pro (Late 2013)

How Power Nap works on your Mac - Apple Support

Configure your Energy Saver preferences like those above. Ignore the first checkbox setting. Use whatever you want for that one.

Xabiablanca wrote:

Strangely despite having latest updates I don't have the Enable Power Nap option, however copied other tick boxes as per screen shot and it seems to be OK now.

That is very odd. Power Nap has been a feature since OS X 10.8.

Apparently you are not missing anything. I was checking the specs of a Mid-2011 iMac for someone else and found this on everymac.

*This system fully supports the last version of OS X 10.8 "Mountain Lion", OS X 10.9 "Mavericks", and OS X 10.11 "Yosemite" except for Power Nap functionality.

It also runs up to High Sierra as you know but without Power Nap among other features.

You may want to boot into Safe Mode then restart normally.

Use safe mode to isolate issues with your Mac - Apple Support

You're welcome.