QuickLook not working in Photos after upgrade to Mojave

A few days after upgrading to Mohave, QuickLook does not work in Photos. It DOES work everywhere else: Finder, desktop, file view (finder), images, docs, powerpoints... all work with quicklook. But when I open the Photos app, highlight a photo, press spacebar, i just get the that annoying "boink" tone when an action is not allowed. Doesn't matter if it is older photos or newer ones. I have a folder of images on the desktop. Works fine there. I restarted; checked Photos preferences; relaunched the finder, etc ... but still does not work in Photos. Any suggestions? Thx.