I recently created an SVG file depicting a toilet, and then I converted that SVG file to DFX online. The converted file, along with all my SU files, resides in my MS OneDrive. The new file displays the SU logo. When I try opening it in SU22, I get an error message "this file does not appear to be a SketchUp file. Am I doing something wrong?
Do you mean you’ve got a.dxf file? If so it wouldn’t be a SketchUp file so no reason to expect SketchUp to open it. Try using File>Import instead. Don’t forget to open the import options and choose the right import units.
Most likely the icon of SketchUp is because windows thinks that a file with the skp extension is a SketchUp file without actual ability to check if it is valid. If you can share the skp here we should be able to tell you whether it is actually a skp and @colin may be able to recover some portions if it is a SketchUp file but is damaged.