I have a UICollectionView which is about the size of the screen. The UICollectionViewCells that it displays are the same size as the collectionView. Each cell has a UIImage
In my case it was just
self.collectionView.allowsSelection =NO;
I had in code.
changing to
self.collectionView.allowsSelection =YES;
fix it.
Are you sure you're not accidentally overriding - (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath
? "Select" vs. "deselect" has tripped me up in the past with Xcode's code completion.