I was having a similar problem, but I think it was due to the fact that I was trying to add a domain that was already in the database. I didn’t really want to add it, I wanted to EDIT it.
The plugin didn’t give me an error, though, it just brought me back to the same screen like nothing went wrong.
I ended up fixing by manipulating the database by hand, but realized my error after the fact.
I hope this helps!
