Icon previews not showing in finder windows

Since recent updates to either High Sierra, or Photoshop CC, I no longer have icon previews of my images showing up. It is very painful, really slow to click on each Tiff or PSD to see the file larger in the window on the right. I need to have that thumbnail icon showing up. But I can't seem to make that happen. I have read threads on Adobe forums that suggested booting up in safe mode, or deleting the apple finder preferences, etc., and I have read threads on this issue here, most recently one that suggested changing Photoshop's preferences to save large file instead of thumbnail in file handling, but my version of PHotoshop (CC2018) doesn't look like his and I don't have the option for 'large file' only thumbnail 'on/off'. Nothing helped. I also primarly use Lightroom, so the exported files are TIFFS or PSD or JPEG from there. My workflow has ground to a halt as I try to review folders of images in the finder to review my exports and others tasks.

Does anyone know what to do next to help me get my icon previews back? please, oh please, say yes. 🙂