Cannot add RSS from showRSS.info

So, I just downloaded this, very excited to replace the TVShows preference pane from way back, however when I try to add an RSS feed from showrss.info it does not allow me to click "Add Feed". If I modify the URL and delete a letter from the showrss.info part, for example, changing https://showrss.info/show/1156.rss to https://howrss.info/show/1156.rss then the button lights up, however if I add a letter, like https://ashowrss.info/show/1156.rss, it remains unlit. Screen caps are attached.