I have been pounding my head against this all night.
The 3rd column is there, but for some reason our images are being sized slightly too large, causing the third column to wrap.
Make sure you’ve set your Catalog Image Size (in WooCommerce > Settings > Products) to 197.
Each column is supposed to be 204px wide, plus margin/padding. Mine comes out to 207px, and those extra 3px are causing my 3rd column to wrap. It’s driving me nuts!
(Yes, I’ve regenerated my thumbnails several times.)
See the problem here:
https://shipshapeboutique.com/products/
If anyone knows why this is happening, please help!