Justinr6,
Welcome to the forum!
It is likely that the Ballcock is not opening properly. It controls the flow of water into the tank. You can purchase replacement ones at your local hardware store.
A note about the valve you opened from the wall... I suggest that after you open the valve the whole way you then turn it a quarter of a turn back, it helps prevent the valve from getting stuck open.
Hope this helps, Jim
'Just a handyman trying to help'