Why can't I authorize my iMac to play purchased music?

Re: I’m trying to authorize my iMac to play purchased music. I get a message saying that I should try again later.

Apple support provides an article online that may be helpful:

Eg: says:

• "You can authorize up to five computers at a time to play your Apple Account purchases.
• Each computer that you authorize counts as one authorization — even if you authorize the same computer multiple times.
• If you have five authorized computers and want to authorize a new computer, you have to deauthorize one of your computers."

There's much more info. in the article itself:

Authorize or deauthorize your computer for Apple Account purchases - Apple Support

Thank you for your reply. Sorry you have been inconvenienced.

With the way technology advances so rapidly, and the way security has had to stay ahead of unwelcome interference, seems the older hardware and software just can not keep up.

My own 2017 computer model can not be upgraded to the newer MacOS versions, although Apple does still provide security updates at present.

Apple Support's article: Identify your iMac model - Apple Support

lists the newest compatible MacOS version for each model.

What's new in the updates for macOS Big Sur - Apple Support

says the latest Big Sur version is:

macOS Big Sur 11.7.10

"This update provides important security fixes and is recommended for all users."

Thank you for your reply, and for letting us know.

Sorry your computer can no longer be authorised by Apple. That's new to me, though I understand some hardware is listed as "obsolete" and no longer supported by Apple, or software in use is no longer compatible with newer OS versions / security updates etc.