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?

this thing pop up.

@JubayerAhmed97 You are trying to load a schematic created in 1.20.5 or later version in some older MC version. Which MC version are you in? The latest 1.21+ versions have an option in the Schematic Manager menu to export the schematic in the v6/1.20.4 format, which allows it to load all the way back in the 1.18 mod versions. (But ofc any blocks that don't exist in any given older version will just turn into air.)