Thanks for all your efforts. I will discuss this with the developper. As mentioned before: I am switching to a different template - but that template has the same kind of problem. So Jevents - Attendance needs to be looked at, I guess (as you suggested).
As to the IP being blocked.... Maybe it wasn't you
(except if you have a constant IP). Perhaps you could PM me your IP not only to unblock it, but to figure out what caused the blocking, so as to check our security measures.
Apologies for the complications.