why won't CS6 open my iMac photo library?

I have a new iMac running OS High Sierra.  I have imported hundreds of photos into the library but when I click on the library a message appears that tells me "Could not complete your request because Photoshop does not recognize this type of file."  And if I click on a phot I get the same message.  How do I get my CS6 to recognize the photos as it did in Windows formats?