Does it happen with all your sgf files or just this one? Is there anything special about it? Where is it from? Any special characters in name for example?
I uploaded one of the original files which was successful and when it uploaded 2 previous attempts suddenly appeared
another file wont upload - server error. Will keep trying. The name is fairly straightforward plus i renamed it but didnt help
Progress i uploaded the most troublesome file to somewhere else and it opened it OK - but there is a txt warning that the sgf file may not be supported in the game comment section. So that may be part of the answer - ( it is a file from an AI called crazystone)