Strange audio problem, iMac i3 21.5 inch

[Tim in Scottsdale]

Guys

Two problems actually. The audio output dies for no apparent reason and has come back once on its' own. The on-screen indicator grays out.

Also, in an effort to fix the audio I brought in an OSX 10.10 Yosemite disc to do a re-install, and I get a message saying Unable to Install, this program is not available from the App Store at this time. That is really annoying; is there a workaround for that?

Is Apple turning into The Software Police or what?

 

[DeltaMac]

If you are running Yosemite now, you can boot to your Recovery system, and reinstall Yosemite through that.
Did you make your own bootable Yosemite installer? Or did you purchase the (free) OS X install from some dodgy site on the 'net?
If you have Yosemite on a bootable USB flash drive (which should work, even if you have no internet connection, so doesn't need to access the App Store), then just option-boot to the flash drive, and install that way. The system files are on the flash drive, and no need to wait for the download (or hope that your internet connection is good enough)
If you have the installer on a DVD, the installer is not optimized for that media, and I do read about users who struggle to get a DVD to work. Also it's common to have a DVD that is just not made correctly.

 

[Tim in Scottsdale]

I don't know how to boot to my recovery system, maybe someone can explain that.

The disc is authentic Apple. It is tied to the App Store somehow, and App Store does not have Yosemite for download.

 

[DeltaMac]

Yes, the only way to have Yosemite available to you as a download at the App Store is if you have previously downloaded Yosemite from the App Store.
Your disc is, unfortunately, not "authentic Apple", as Apple has not officially provided ANY version of the Mac operating system installer on a DVD since Snow Leopard (OS X 10.6.x). If you purchased it somewhere, then someone downloaded the installer from Apple, and created a DVD from that installer. That's what you have, and it's not an "authentic Apple", even though it might work.
But, your DVD is improperly made, if it asks for access to the App Store.
MUCH better is a bootable USB installer. Still not "authentic", but will work. You can also buy USB installers. There's several different choices on Amazon, and other sites as well. NONE of those media come from Apple, either - only the software itself, unless you find one of the Apple-made USB thumb drives that came with some Macs when Lion was new.

Here's your info about how to boot to the recovery system, which will likely help you more than that DVD does.
https://support.apple.com/en-us/HT201314
If you are currently running Yosemite, the recovery system will allow you to reinstall Yosemite.
If you are running something newer than Yosemite, but your Mac shipped new with Yosemite, you can still install Yosemite, by booting to Internet Recovery.
There's a small difference in the boot if you need to boot to Internet Recovery, if you need that. It's also covered in that same article.