Strange bug or setting i can’t figure out

Im new to illustrator, but something i have been able to do for weeks no longer works, and i cant figure out why. 

When using the pen tool, for example, if you are zoomed in closer to your canvas, with just a little of the gray artboard outside the canvas, and try to drag and pull downward to create a rounded path, typically the pointer would cause the arthoard to scroll downward to continue dragging your path. 

However, since yesterday, this is no longer the case. When i try to pull downward to create my path, it just stops at the current edge of the artboard. I have to stop and zoom out to be able to drag down far enough to create my rounded path. For some odd reason, i can still pull upwards and it works normally. 

anyone have any thoughts as to why? I tried restarting the app, but no go. I may have inadvertently hit a keyboard shortcut, but i cant figure out what it might be.