NW.js and Greenworks are both deprecated and have been removed from the latest releases. Our official advice is to use Windows WebView2 and the Steamworks addon which have continued support.
The Steamworks addon should work out-of-the-box and I fairly regularly test it and it generally looks fine. I would guess you've done something wrong, but it's hard to tell unless you share a project. My best guess is that you should test with development mode enabled. It sounds like you had that turned off, and if you turn it off, I believe the game must have actually been published to Steam for it to work, and so if you haven't yet done that, it won't work. So use development mode until then.