Cannot acess the onion skin view

hello everyone, up untill recently, my onion skin view doesnt show so i cant make use of the advanced onion skin functions it provides. i usually acessed it from the windows tab >onion skin but now i click on the onion skin and nothing happens. ive tried the onion skin button in the tools tool bar and it onlt brings the normal onion skin which i donot want, it can not vary opacity like the advanced one. please help!