something wrong with my client?

[Chris5170xD]

when either my bro and I attack another player ... shooting them in the head chest etc.... they dont take any dammage ... but they can hurt us ... and we can hurt each other ... we are playing on a network together....

and suggestions?

Eather desync, where the player is walking without moving legs, reloads, but doesn't shoot.

Or, lag. Which is where it seems to you that someone is there, but they just passed that place.