When opening a schematic with the extension, .schematic does not load the schematic and only remains invisible, it only happens with the .schematic files, in version 1.20.4, latest version of fabric, and the version of schematic I am using is 0.17.3

Do you get the placement bounding box at all? Or do you get an error when trying to load it? Can you send that file, or does it happen with all schematics of that type?