iMac (21.5-inch, Mid 2011) won't update software. HELP

You will need to upgrade your version of Mac OS to the most current version a 2011 iMac supports. This is Mac OS 10.13.6. 2011 & earlier iMacs cannot go beyond 10.13.6 as they do not have GPUs that support Metal. You can still get 10.13.6 from the Mac App Store.

As for your MBP, that does support Metal and you can upgrade it to Mojave 10.14.x.

Check to see that the version of Office you have (it has been around for many years with many many versions) and then check to see what it's system requirements are. Once you are armed with that information and you know what version of Mac OS is needed then you can begin implementing some plans.

You would need to go looking to proper locations to get the installer from Apple.

•Upgrade to macOS High Sierra - Apple Support

https://support.apple.com/macos/high-sierra

Once that's done, correctly, you may have need for newer applications; also if you

do not already have & use backup(s) such as external drives, & Time Machine, start.

What is it you can't update, exactly?

A 2011 iMac won't run Mojave. It WILL run High Sierra and the current version of iTunes.

It's almost 7 years old. Technology marches on. Your iMac is still perfectly usable.

My post was intended to be instructional. We cannot help you if you do not provide pertinent information such as what version of Mac OS is installed, without this basic info we cannot help.

Good luck though!

We are all end users like yourself, you are not addressing Apple on these forums. You have not stated what version of Mac OS is currently installed on your iMac so I'd suggest before posting again that you read the Terms of Use you agreed to and also Writing an effective Apple Support Question.

If you have feedback for Apple please post at www.apple.com/feedback.