Joobathann

I'm playing on a modded LAN server with two other friends through Radmin VPN and me and one friend can't hit mobs but the 2nd friend is easily able to hit mobs. One time I was able to hit mobs but then I died and I couldn't hit the mobs again. All the players are operators. I have no idea what would cause this, I contacted the friend that help me set this up and she said she has no idea what to do either. Any solutions found?