Just to be sure that we're talking about the same thing, are you referring to Preview or QuickLook? When you hit the spacebar, you invoke QL. Preview is Apple's PDF viewer and you would need to actually launch it to see a file.
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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