Can’t use any attack weapons or potions

I can’t attack any players in my world and it’s really frustrating. A person in my world started killing my foxes and I couldn’t attack him because my arrows went through the person, sword had no effect or showed that it was even doing damage, and my potions didn’t do any affects when thrown at her. I even tried the potions on myself and NOTHING happened. I have not changed any settings to prevent attacking other players and I don’t know what the problem is.