Sermon Manager Podcast Trouble

I am wanting to do a podcast, however, I am having issues when using the Sermon Manager plug-in. The website is https://www.acssevier.com. When I go to validate my podcast feed url, it says this:

Sorry

This feed does not validate.

Server returned HTTP Error 404: Not Found [help]

HTTP error with content that looks like a feed [help]

line 18, column 2: href must be a full URL: [help]

<itunes:image href=”” />
^

I am absolutely confused as to what I need to do. I am not good at this stuff at all, and everything I research online seems to require a strong knowledge of how to podcast in the first place.

Please help!