I want to use software which takes GFF file formats as input, but I've got GTF files. http://www.sequenceontology.org fails. So if anyone can provide me with a script or suggest tools, that would be very helpful .
See http://www.sequenceontology.org/cgi-bin/converter.cgi for the link to download the script for local use. If their server is failing, it may be that your GTF is just too large for their web tool.