*Read your skill to check if you are allowed to use her effect
*Maybe the monster you tried to equip can't be targeted
*The monster has to have more attack than v vamp
*She has to be normal summoned to activate her effect.
*While on the field to proc her effect again another vamp has to be normal summoned
*She can miss timing
I was using vamps earlier today and had no problem using her usually the part people omit is normal summoning her or trying to use her against a monster with the same atk as her though you have already tested that
The most likely explanations are:
1) You missed the timing
2) Another effect (or skill) prevented you from activating the effect. Maybe Forbidden Chalice or Warning Point got used before and you missed it
But to answer OPs original question: No, cards usually don't get nerfed.
Vampire Vamp
Troubleshoot
