why does my dvd player all of sudden say "supported disc not available" for dvds i have played in the past

Is that "DVD Player," the application to play DVD movies, and you are trying to play movie discs? Or are you refertring the optical drive as a "DVD player" and the problem is with ALL discs that you insert?

If you have only been trying movie discs, what happens if you insert a "data" disc, such as a software installation disc? Or a music CD?

Are you using a commercial disc or a burned disc?

Quit DVD Player and then using Disk Utility, run Repair Permissions on your hard drive.

 Cheers, Tom 😉

These are standard DVD movie disc, and not Blu-ray discs, correct?

Since music CDs work, lets hope the optical drive itself is OK. Open System Preferences CDs & DVDs pane. For the setting When you insert a video DVD, if Open DVD Player is currently selected, try changing it to Ignore.

When you insert a movie DVD now (with DVD Player NOT running), it should just be ignored and mount to the Desktop. Is that what happens? Is so, what happens when you run DVD Player manually and try to play the movie?

That's not good... Since DVD Player is no longer involved, it sounds like a problem with either the OS or the hardware.

Music CDs are still OK? What happens with a DVD that is not a movie, such as a Mac OS X installation disc, or other disc that is a "data" DVD?

Ditto here as well....... Some ""Super Drive""..... New IMac, latest software, and unable to display simple home videos that I copied from a VHS tape to DVD-R. I can play the DVD on a TV using an old DVD player. Tried everything.....AND I MEAN EVERYTHING. Jobs is shaking his head over the lack of support and compatibility. Add to that the dumping of Aperture and IPhoto.....hummmmmmm

A "new" iMac does not have a built-in optical drive, so are you using an external optical drive connected to USB? Does it read other types of discs, such as music CDs and software installation discs?

As I previously stated - I am using the "Apple Super Drive"

I'm having the same problem lately. I have a mid 2010 21.5" iMac with an internal SuperDrive running Yosemite. I tried putting in "Dawn of the Planet of the Apes" and "The Giver" rented from RedBox. Both spin sputter for a bit and then eject the disk back out. So, it never mounts and no software (Finder, Disk Utility, DVD Player) ever gets a chance to see it. Both play fine in a 15 year old DVD player, and my purchased copy of "The Dark Knight" mounts just fine in the iMac. So, I have to assume that something is being done to the DVD's that rental companies are given to prevent them from mounting or something.

Not having any luck on Google trying to confirm that.

I guess I need to amend this. Both DVD's play fine in a early 2011 13" Macbook Pro with the internal SuperDrive. It's running Mavericks still and has a "MATSHITA DVD-R UJ-8A8". The iMac has a "OPTIARC DVD RW AD-5680H". Not sure if it's the drive, the OS, or what (although I will say I'm fairly certain I was having this problem on the iMac before Yosemite, so it's probably not the OS).

A "Super Drive" is also what the mechanism is called (by Apple) when it is install as a built-in component. So saying "Super Drive" does not necessarily imply it is external.

And, as I previously asked, "Does it read other types of discs, such as music CDs and software installation discs?"

I have the same problem. Stock iMac, no mods. Plays standard (purchased) DVDs, CD-Rs, music, etc. Will not play Redbox DVDs--drive makes a few spin-up sounds and ejects the disk after 10 seconds or so... If I manually open DVDPlayer, it gives me the "Supported Disk Not Available" error.

Anyone have any useful information regarding this particular problem???

Poor media are the likely cause. They can have poor coatings that wear off. Most of us here recommend Verbatim, Maxell and Taiyo Yuden media.

But start by cleaning the Superdrive using a proprietary lens cleaner with tiny brushes.