quickbooks 2015 not working

It should be able to tell me before if it can tell me after.

It's not Apple's responsibility to check every software application that's in existence to see if it is compatible with the new system. That's the developer's responsibility and why Apple provides beta versions to all developers so they can update their products. So direct your wrath at Quicken, not Apple. They had plenty of time to come up with a compatible version but evidently decided not to.

This is much simpler if you're already in Sierra. Go to this page on Intuit's site. If the version of QuickBooks showing isn't QB 2015 for Mac, click the Change button and select it.

Click the Download button. You'll get this choice:

Click the appropriate link. It will download the file QuickBooksProMac2015.dmg. What you get is the full QB 2015 Mac app. It's already the latest version, 16.1.12.1564 R13, with a creation date of February 21, 2017 at 2:00 PM. So you should be able to simply copy the app to the Applications folder and launch it.

I really do like Apple but this is total BS that it tells you after the fact that your software is incompatible. I now need to either pay tp update Quickbooks which I do not want to do or now have to back to El Capitan. When updating the OS it should tell you beforehand so one can decide how they want to proceed. Ridiculous.

How can it tell you before it's installed? It has to be installed so that it can examine the apps and evaluate them.

As KiltedTim pointed out earlier it's the user who has the responsibility to determine if their apps will be compatible with the new system. There are a number of ways to do that: contact the developer of those apps and ask or go to RoaringApps.com and see if the app has been tested by other users and reported.

But shouldn't it give you the choice to proceed with the update or go back to the previous version?

This is my wifes mac so I'm not that familiar with it.

Can i revert back to El Capitan and regain use of our quickbooks?

Intuit did release an update for QB Mac 2015 so it will run in Sierra, but, since a non-updated 2015 copy won't launch in Sierra, you have to update the app before upgrading to Sierra.

The quickest solution would be to copy the main QB app to a Mac running El Capitan or Yosemite and update it there. Then bring the updated app back to the Mac running Sierra. Make a backup of the updated app so in case you need to erase and reinstall Sierra, you'll already have a copy of QB 2015 that will launch in Sierra instead of starting the update loop over from the original disk or purchased download.

This may help: macOS Sierra: Revert to a previous macOS version

Quicken was one of two applications that I was informed at the end of the install would not work with Sierra and were moved to an Incompatible software folder by the install application.

Maybe you should start checking to see whether the 3rd party software you're using is compatible with a major OS upgrade before you upgrade.

Sorry, but I disagree. I shouldn't have to do that, especially these days and especially if its going to tell me after the fact. It should be able to tell me before if it can tell me after.

I don't necessarily disagree with that but if it can tell me after I install that its not compatible it should be able to tell me before is my point.

Then tell Apple how you feel. This is not Apple. This is a user forum.