It appears that the visual previews is not working with images shot with the new Sony A74 camera. I have no problem with images shot with the 61mp Sony A7R4, or the A7r2 & A7s3. Anyone else experienced this problem?

In order for the visual previews to work, you need to have installed a version of the Adobe DNG Converter that supports that camera. For new cameras you might have to wait until adobe releases such a version.