The latest version of Yosemite doesn't support iPhoto and my iPhoto library says it has already been migrated, it hasn't. Its 256GB in size, thats a lot of photos I can't access?
MacBook Pro with Retina display, OS X Yosemite (10.10.4)
and my iPhoto library says it has already been migrated, it hasn't.
Please elaborate a bit. What makes you think that the library has not been migrated?
If Photos migrated your iPhoto Library, the filename extension will change to ".migratedphotolibrary". What is the filename extension of your library?
Photos should have created and library in the same folder as your iPhoto Library with the filename extension ".photoslibrary".
Are you seeing a library with an icon like thin in your Picture folder or in the same folder as your iPhoto Library?
The latest version of Yosemite doesn't support iPhoto
Apple released a compatibility update for iPhoto. You need to update to iPhoto version 9.6.1. See this user tip on how to update, if you missed the update:
Get iPhoto 9.6.1 if you didn't update before OS... | Apple Support Communities
Library hasn't been migrated but says it has and now can't open
