Subscription Management Page blank

I run https://imnotobsessed.com. I don’t have a HIGH commented blog. But I do get quite a few responses on certain posts. When people subscribe to comments, they typically email me asking me to unsubscribe them because they get tired to receiving the mail. I have no control over this because when I try to access the subscription mgt. page it is blank.

What do I need to download? Am I missing a php file?
Thanks so much
??
Vera