Updated to Yosemite, I have Aperture 2.1.4 which worked fine on Mavericks. It is now saying I can't use it on Yosemite. Any help?

Yes. Only Aperture 3.6 is compatible with Yosemite. Upgrading from aperture 2 to Aperture 3 is a paid upgrade. You can buy the upgrade from the AppStore.

You have been lucky, that Aperture 2.1.4 worked well for you. There have been compatibility issues with Aperture 2.1.4 since MacOS X 10.7 Lion came out. The last compatibility update Aperture 2.1.4 was for MacOS X 10.6.8. Snow leopard is the last MacOS X version, that officially supports Aperture 2 well. Yosemite is the fourth MacOS X upgrade, since Aperture 2 has been replaced by Aperture 3 in February 2010.

Be sure to keep a backup of the Aperture library, before you upgrade. The upgrade will rebuild the library in a new format. See the Release Notes, i.e. the last paragraph, "A Note on Upgrading" Aperture 3.6 Release notes http://support.apple.com/kb/TS2518

phishincub wrote:

Thank you, problem is, I didn't know any of this before updating to Yosemite so I can't even open Aperture at all to rebuild my library prior to upgrading Aperture. Any work arounds that you know of?

Then let's hope, that that the Aperture library has no glitches and try to upgrade without repairing before. Keep a backup copy of the Aperture library, just in case, before you try the upgrade.

Time Machine backup is fine. If you have space on an external drive,you can simply drag your Aperture library to that drive in the Finder to make an additional backup copy.

To buy the Aperture upgrade, launch the AppStore, click the "Store" menu, and check, if you are signed into the store with the AppleID you want to use for the purchase. Open the first tab of the AppStore, the "Featured" tab, and enter Aperture into the Search field. Then buy the upgrade.