When GiGa.GG is done uploading a file, a preview of the file is computed on the GiGa.GG servers.
The file will appear with a 'Computing preview' tag during this process.
A file under 'Computing preview' can't be opened until the preview is finished.
The process may take a few seconds or up to an hour depending on the file size and on the servers occupation.
If the 'Computing preview' label does not disappear while you believe it should have, refresh your browser page.