Wrong RSS Feed

On my site my RSS feed is not working. Every time I go to https://www.silvys.com/discast/index.php/feed/ I get the error No input file specified
. Yet if I used the url https://www.silvys.com/discast/feed I get my RSS feed. My problem is that my podcast is listed on iTunes using the old feed silvys.com/discast/index.php/feed and I can’t tell iTunes to use the new URL because I can’t access the old feed to put in the needed code. Any ideas on how to get rid of the No input file specified? Thanks in Advance!