My Neewer Speedlite 750II is not working

I am having lots of trouble with my flash.
I attached it to my camera and the red light was pulsing, but later it just stayed fixed and the pilot button is not working either. I am not sure if it’s an internal problem or my camera settings (i am new to flash so I am not sure how it is supposed to be).

A few months ago I used in TTL and it worked just fine, but right now I’ve tried several options, including, resetting my camera settings, resetting my flash settings, silent mode, changing my shutter speed, but nothing.

The flash seems to be communicating with my camera because all the info from it is reflected on the flash screen, but I don’t know what else to try.

Any suggestion?