I have Xara Photo & Graphic Designer 18.5.0.62892 DL x64 Aug 11 2021. With all previous versions of Xara I've been able to Preview or Publish my WEB from the File menu. I can't with this version and the app is set up correctly. I downloaded another version but afraid to install; don't want to screw anything up.
Strange that you could publish a web page before because P&G Designer does not normally have that feature. It's called Photo & Graphics Designer, not Web Designer. Web design (except for graphics) is done with Xara Web Designer or Xara Web Designer Premium, or the total combined product, Xara Designer Pro X.