Unable to install macOS updates on MacBook Pro

It sounds like you might have an older MacBook Pro that has hit "the end of the line" and that is not compatible to run recent versions of macOS.

Still, you have not given us any details to work with. Which MacBook Pro do you have, and what version of macOS is it running now? What are you trying to do with the machine that would require "the latest updates"?

Identify your MacBook Pro model - Apple Support

If it runs the applications you need, you can keep using it.

In many cases, that will mean having those applications already. Vendors such as Microsoft and Adobe dropped support for High Sierra long ago.

Note:

• There is an older version of Firefox (115 ESR) that has received multiple "stays of execution" – and now will be receiving security updates from Mozilla until March 2027. (Mozilla Support – Firefox users on macOS 10.12, 10.13 and 10.14 moving to Extended Support Release). This is probably the best you are going to get for High Sierra – and it may not be good enough for all Web sites, especially banking Web sites.
• The current version of LibreOffice will not run on High Sierra. There is an archive of old, unsupported versions, and The Document Foundation Wiki – Documentation/System Requirements may be able to help you find the latest unsupported version that will run on High Sierra.
• When it comes to photo editors, I'm not sure if you have many options left other than the commercial program GraphicConverter 12. Affinity Photo V1 ran on High Sierra, but was withdrawn from the market when V2 came out. The free parts of Affinity Studio require Catalina, and the GIMP requires Big Sur.

Re: “… 22.5” mid 2011 model …”

There’s never been a 22.5” MacBook period.

Maybe it’s a iMac (21.5-inch, Mid 2011)

If so, it can only run up thru High Sierra.

Identify your iMac model - Apple Support

Re: “22.5” mid 2011 model”

There is no such thing as a MacBook Pro with a 22.5” screen. If by any chance, you are referring to a 21.5” mid-2011 iMac desktop computer, High Sierra is the end of the line. That computer is far too old to run the current version of macOS or anything close to it.

Identify your particular model from the URL Servant of Cats provided …

… the details for your model then cite the “latest and greatest” MacOS which your hardware is capable of running.

it's really up to the app developers which version of macOS they wish to have support for

seems many like microsoft only choose to support 3 macOS versions so if one wish to rely on support from such third party software companies then, yeah you sort of need to get a newer computer, apple sort of release a new mayor macOS version each year, and if ms only choose to support 3 then that do not mean you need a new mac every 3. year as macs get updates for several years after release, as my link to required macs show.

the next macOS after high sierra is mojave

macOS Mojave - Technical Specifications - Apple Support

it your mac do not meet its requirements

If it runs the apps you need it to, it’s sufficient for your needs.

If you need to run newer apps needing a newer MacOS - or access many financial web sites — your 15-year old computer might be ready for retirement.

Rudegar wrote:

if ms only choose to support 3 then that do not mean you need a new mac every 3. year as macs get updates for several years after release, as my link to required macs show.

In the case of the OP's iMac (21.5-inch, Mid 2011), introduced in May 2011,

• That model originally shipped with Mac OS X 10.6.6 or 10.6.7 (Snow Leopard).
• It can run anything up to macOS 10.13.6 (High Sierra), so it received seven major updates. Lion and Mountain Lion cost $20 each if purchased in electronic download form, and ones after that were free.
• High Sierra fell out of "the most recent three" when Apple released macOS 11 (Big Sur) in November 2020.

Thus, that iMac was able to run one of the "most recent three" for about nine and a half years.

What car or navigation system are you using? Some manufacturers offer USB or SD card updates that don’t require a newer Mac. Also, Firefox 115 ESR is probably the newest browser option available for High Sierra, and it may work with your map update site.