The hit cooldown bar does not appear.

It worked and then suddenly stopped appearing. I haven't tried redownloading Minecraft. I use many different clients and all of them it does not work including the official launcher. It started happening once i first used a different client. I thought it was weird the client did that. However when i went onto another client it was also there.

For further clarification:  
that bar underneath the crosshair. The crosshair appears but not the bar.