Unable to update iMac

Hi,

A couple of things: first please never post private information in a public forum, this includes:

• Serial Numbers
• Addresses including home, business, email, etc.

Also, when posting we need to know which model year iMac you own as they have been in production since 2009, over 12 years in a wide variety of configurations. Finally, please let us know the current version of Mac OS installed.

If you are unsure of the model year and version of Mac OS installed, please click the Apple Symbol in the upper left of the display and then click About this Mac and you can find the information you need there.

Welcome to the Apple Support Communities.

Using this Apple Support article as a guide, About System Information on your Mac - Apple Support, please let us know what year your Mac is and what version of macOS you are currently using.

Jack