Categories are not showing on WordPress dashboard!

categories are not showing on WordPress dashboard!!
I dont know how but i cannot see my categories in woo-commerce product categories option.
the rare thing is that if i am making a new category and then refreshing my page its gone again!
I also tried to enter same name categories which i made earlier, I also tried to keep the slug name same but there was an error that it exists.
If it Exist so where will i see that??
Please help me !!