What Part do I need to replace?

My washer all of a sudden stopped working, no warning of anything going wrong.
It will not fill with water, however if I manually pour water into the tub it will start agitating and go through it’s normal cycle with spin. It just won’t fill up with water.
I need to know what needs to be replaced to fix this problem. Any parts I buy for this are non returnable. I want to get it right the first time. Also maybe it’s not a matter of a new part, maybe I am over looking something simple.
I cannot afford a new washer at this time. Everything else seems to be fine with it, it just won’t fill with water.
Thank You to anyone who can help me with this.
Chris