I experienced some downtime on my blog due to some problem with Blogger FTP publishing feature. It is unfortunate to see that Blogger is not able to handle forum support anymore except major percent of the blogs stop working.
My atom.xml and rss.xml files were having 0 file size although the internal blogger rss feed for my site was working. I fixed the problem by going to Settings/Site Feed and placed a leading dot (.) before the slash. So your path will start with “./”.
I hope this works for you!