Did you download just the one file, or did you download the whole zip and unzip all of the files into a folder?
I’ve basically downloaded the whole zip file and then went and opened the Fireware Arduino and it did open ! But I’m using MacBook
Did you first extract the files to disk, or did you open the .ino file from the ZIP? You have to have all the files on disk and if you open the .ino file from the ZIP file, most operating systems only extract the file you open, not all of the others. Are you able to see all the files in a folder after you delete the zip file?
This can help.